Chapter 4

Networking and the Internet

2

Chapter 4 Networking and the Internet

41 Network Fundamentals 42 The Internet 43 The World Wide Web 44 Network Protocols 45 Security

3

Network classifications Networks--Isolated computers can be

connected to work together via networking Classifications Local area network (LAN) --on a single

building or a group of buildings Such as university campus a manufacture plant or the like

Wide area network (WAN)mdashone LANs can be connected to other LANs over any distance through telephone lines or radio waves

Such as city

4

Network classifications Closed or proprietary--held by an

individual corporation like Novell networks

Open--networks have the ownership in the public domain like the Internet

5

Network classifications

Characteristics of Network TopologymdashThe geometric

arrangement ProtocolsThe rules and encoding

specifications for sending data Media---Devices are connected by

twisted-pair wire coaxial cables or fiber optics or radio waves

6

Network topologies Ring Bus Star Irregular

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

2

Chapter 4 Networking and the Internet

41 Network Fundamentals 42 The Internet 43 The World Wide Web 44 Network Protocols 45 Security

3

Network classifications Networks--Isolated computers can be

connected to work together via networking Classifications Local area network (LAN) --on a single

building or a group of buildings Such as university campus a manufacture plant or the like

Wide area network (WAN)mdashone LANs can be connected to other LANs over any distance through telephone lines or radio waves

Such as city

4

Network classifications Closed or proprietary--held by an

individual corporation like Novell networks

Open--networks have the ownership in the public domain like the Internet

5

Network classifications

Characteristics of Network TopologymdashThe geometric

arrangement ProtocolsThe rules and encoding

specifications for sending data Media---Devices are connected by

twisted-pair wire coaxial cables or fiber optics or radio waves

6

Network topologies Ring Bus Star Irregular

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

3

Network classifications Networks--Isolated computers can be

connected to work together via networking Classifications Local area network (LAN) --on a single

building or a group of buildings Such as university campus a manufacture plant or the like

Wide area network (WAN)mdashone LANs can be connected to other LANs over any distance through telephone lines or radio waves

Such as city

4

Network classifications Closed or proprietary--held by an

individual corporation like Novell networks

Open--networks have the ownership in the public domain like the Internet

5

Network classifications

Characteristics of Network TopologymdashThe geometric

arrangement ProtocolsThe rules and encoding

specifications for sending data Media---Devices are connected by

twisted-pair wire coaxial cables or fiber optics or radio waves

6

Network topologies Ring Bus Star Irregular

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

4

Network classifications Closed or proprietary--held by an

individual corporation like Novell networks

Open--networks have the ownership in the public domain like the Internet

5

Network classifications

Characteristics of Network TopologymdashThe geometric

arrangement ProtocolsThe rules and encoding

specifications for sending data Media---Devices are connected by

twisted-pair wire coaxial cables or fiber optics or radio waves

6

Network topologies Ring Bus Star Irregular

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

5

Network classifications

Characteristics of Network TopologymdashThe geometric

arrangement ProtocolsThe rules and encoding

specifications for sending data Media---Devices are connected by

twisted-pair wire coaxial cables or fiber optics or radio waves

6

Network topologies Ring Bus Star Irregular

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

6

Network topologies Ring Bus Star Irregular

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

7

Figure 41 Network topologies

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

8

Figure 41 Network topologies (contrsquod)

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

9

Connecting networks Networked computers can be connected in a

hierarchical fashion as an internet DARPA (Defense Advanced Research

Projects Agency) initiated the Internet in 1973

Interconnection of networks are achieved through routers or proprietary gateways(earlier terms for routers)

Bridge connects two compatible networks Router connects two incompatible networks

Resulting ldquonetworkrdquo is called an internet

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

10

Figure 42 The distinction between a bridge and a router

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

11

Inter-process communication Clients a client makes requests to

servers1048708 Servers a server performs the service

and sends replies back to the client (s)ExA machine with high-capacity disk

drive contains all the records of other machine

(servers the othersmdashclients)

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

12

Figure 43 The clientserver model

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

13

Inter-process communication Inside the same machine or among the

machines over the networks

Client-server One server many clients Server must execute continuously Client initiates communication

Peer-to-peer Two processes communicating as equals Peer processes can be short-lived

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

14

Figure 44 The clientserver model compared to the peer-to-peer-model

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

15

Distributed systems Systems with parts that run on different

computers Multiple independent computers

communicating over a network to accomplish a common task Infrastructure usually provided by

standardized toolkits Example Enterprise Java Beans from Sun

Microsystems Example NET framework from Microsoft

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

16

1 Which of the following is not a way of classifying networks

A WAN versus LAN B Closed versus openC Router versus bridge D Star versus bus

ANSWER 2 Which of the following is not a means of performing interprocess communication

over a network

A Clientserver B ICANN C Peer-to-peer

ANSWER

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

17

The Internet The Internet one internet

spanning the world Started by DARPA in 1973 Today involves millions of machines

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

18

Internet Architecture Domain = network or internet controlled

by one organization Gateway = router connecting a domain

to the cloud cloud = the rest of the internet

Domains must be registered by their owners Internet Corporation for Assigned Names amp

Numbers (ICANN) serves as registrar

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

19

Figure 45 A typical approach to connecting to the Internet

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

20

Strategies for connecting to the Internet

Large organization buy a direct connection

Small organization or individual link domain to the domain of an ISP ISP = Internet Service Provider

Individual temporarily link computer into ISPrsquos domain

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

21

Internet Addressing IP Addresses IP address = 32 bit identifier for a

machine Network identifier = part assigned by ICANN Host address = part assigned by domain

owner Dotted decimal notation = standard for

displaying IP addresses Example 192207177133

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

22

Internet addressing host names Host name = mnemonic name

Example mymachineawcom Domain name = part assigned by a registrar

Example awcom Top level domain = classification of domain owner

By usage ndash Example com = commercial By country ndash Example au = Australia

Subdomains and individual machine names Assigned by domain owner Domain owner must run a name server

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

23

Connecting networks InterNIC(Internet Network Information

Center) regulates the 32-bit address of domains and thus each machine= network identifier (x-bit) + host address (32ndashx -bit)1048708

The network identifier of the mnemonic domain nameldquonthuedutwrdquo is ldquo140114rdquo determined globally

while ldquonyxccrdquois ldquo631rdquoassigned locally by the Computer Center of NTHUrArr

The host machine ldquonyxccnthuedutwrdquohas an address ldquo140114631rdquo

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

24

Internet applications Electronic main (e-mail) File Transfer Protocol (FTP) Remote login telnet etc World Wide Web

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

25

Electronic mail Mail server set up by domain

owner Mail sent from domain members goes

through mail server Mail sent to domain members is

collected by mail server

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

26

If the network identifier of a domain in the Internet is 11548 how many unique IP addresses are available for identifying machines within the domain

A 4096 B 16384 C 32768

D 65536

Which of the following is not an application of the Internet

A FTP B Email C Telnet D RING

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

27

World Wide Web

Atop the Internet the WWW allows the propagation of multimedia documents

--The hypermedia documents consists of hypertexts texts audiovisual contents links

Server disseminates hypertext (or hypermedia) documents Web site = all hypertext documents controlled by

one organization or individual Usually all at same internet address

HTML = language of hypertext documents Other content can also be disseminated

Example images

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

28

World Wide Web implementation Web server provides access to

documents on its machine as requested Browser allows user to access web

pages Hypertext Transfer Protocol (HTTP)

communication protocol used by browsers and web servers

Uniform Resource Locator (URL) unique address of a document on the web

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

29

Figure 46 A typical URL

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

30

Hypertext document format

Entire document is printable characters

Contains tags to control display Display appearance Links to other documents and content Dynamic functions

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

31

Figure 47 A simple Web page

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

32

Figure 47 A simple Web page (contrsquod)

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

33

Figure 48 An enhanced simple Web page

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

34

Figure 48 An enhanced simple Web page (contrsquod)

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

35

Extensible Markup Language (XML)

XML a language for constructing markup languages similar to HTML A descendant of SGML(Standard

Generalized Markup Language) For math multimedia music and Web

pages

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

36

Figure 49 The first two bars of Beethovenrsquos Fifth Symphony

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

37

Dynamic web pages(ie search)

Client-side(specifies topic of interest) Examples java applets java script

Macromedia Flash Server-side(identifying documents)

Common Gateway Interface (CGI) Servletsmdashallow clients to execute

programs units in servers PHP(personal home page)

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

38

Network protocols transmission control

Token ring one-way communication around ring network

Ethernet Uses carrier sense multiple access

with collision detection (CSMACD) Popular for bus networks Like a conversation in small group

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

39

Figure 410 Communication over a ring network

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

40

Figure 411 Communication over a bus network

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

41

Figure 412 Package-shipping example

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

42

Figure 413 The Internet software layers

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

43

Figure 414 Following a message through the Internet

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

44

Internet software layers

Application layer Example browser

Transport layer TCPIP UDP Network layer handles routing through the internet Link layer handles actual transmission of packets

Token ring or Ethernet

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

45

Delivery of messages The transport layer takes the message from the

application layer packages them with additional tags (50+bytes including sequence hellip) into packets of a size compatible with the beneath network layer and hands over to the network layer1048708

The network layer will properly forward these packets to the very network specified by the application layer1048708

The same prefix of both addresses hArron the same network1048708 Different rArrthe network layer appending the address of a

router in the current network sends the packets to that router (maybe intermediate routers) 1048708

The link layer does the actual transmission between machines and routers by local addressing system with additional wrapping rArrstriped off at the message destination

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

46

TCPIP Protocol Suite

It is the network layer to determine the destination of the next hop (network)1048708

The routing table in the network layer contains the final destination addresses and intermediate addresses [NAT IP address vs Link address]1048708

The information in this table routinely exchanges and propagate through the Internet1048708

Packets of the same message may travel along different paths1048708

Once all packets of the message are received (using sequence ) the target transport layer hands it over to its application layer [complete delivery]1048708

The response time of the Internet is rather instant in milliseconds1048708

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

47

TCPIP Protocol Suite

The TCPIP protocol suite defines a collection of protocols beside TCP and IP1048708

IP(Internet Protocol) defines the network layer service1048708 --Hop count TTL (time to live 64) decrement per hop forwarding

avoiding circling1048708TCP(Transmission Control Protocol) defines a reliable transport

service1048708 --Two ends first build an acknowledged connection and confirms each

subsequent packet delivery in sequence1048708UDP(User Datagram Protocol) defines a more efficient but less reliable

transport service1048708One end sends the data merely to the destination address regardless of

its reception1048708ISO (International Organization for Standardization) develops the OSI

(Open System Interconnection) reference model using 7 layers ndashApplication Presentation Session Transport Network Data Link amp Physical

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

48

Figure 415 Choosing between TCP and UDP

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

49

Which layer of the TCPIP hierarchy actually transmits a messageA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy chops messages into units whose size is compatible with the InternetA Application B Transport C Network D Link

Which layer of the TCPIP hierarchy decides the direction in which message segments are transferred across the Internet

A Application B Transport C Network D Link

Which layer of the TCPIP hierarchy presents incoming messages to the computer user

A Application B Transport C Network D Link

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

50

Network security Connecting to the networks a machine becomes

accessible to the general public1048708 Unauthorized access attack on confidentiality1048708 Protection on personal information Vandalism malicious acts from hackers computer viruses or

network worms Computer Virusmdasha program segment that attaches itself to other

programs in computer systems Wormsmdashan autonomous program that transfers itself through a

network taking up residence in machines and forwarding copies of itself through network

1048708

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

51

Network security Privacy of communication

Public-key encryption Public key and private key (asymmetric)1048708 A and B each have pairs of public key and private

key PA pA and PB pB1048708 --Private keys are held by individuals while public

keys are known to the party1048708 Authenticated receiver (only B has pB to decrypt the

received data)1048708 Authenticated sender (only A has pA to send that

encrypted data)1048708

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

52

Network security

Integrity of machine exposed to internet Attacks viruses and worms Defense firewall Firewall software that filters the traffic

entering or passing through a machine(network layer to reject traffics from an entire domain or a specific IP)

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address

53

The primary purpose of which of the following is not the enhancement of security

A ICANN B Firewall C Encryption D Public key

Which of the following is not a means of referencing entities on the Internet

A URL B IP address C Anonymous FTP D Host address