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Transcript of Room 817, Ho Sin Hang Engineering Building Email: [email protected]
© P.C. Wong Transparency No.2-1
Room 817, Ho Sin Hang Engineering BuildingEmail: [email protected]: http://learning.hkedcity.net/ieg1001/
Information Engineering in Information Engineering in SocietySociety
Chapter #2 : The Internet and Chapter #2 : The Internet and TCP/IP TCP/IP
Prof. P.C. Wong Department of Information EngineeringThe Chinese University of Hong Kong
2003
© P.C. Wong Transparency No.2-2
What do you need to know?
1. Internet – a network of networks.
2. Protocol – data format, procedures for communications.
3. Internet hosts have domain names and IP addresses.
4. IP address – 4 byte represented by (n.n.n.n)
5. Information is carried by IP packets up to 64 Kbytes each.
6. IP packets are routed independently to the destination (packet switching) based on the IP address on the packet.
7. There are two common transport protocols – TCP and UDP.
a. TCP – connection oriented.
b. UDP – connectionless (datagram)
8. Applications (e.g., FTP) are run on top of TCP or UDP. Application data is put into TCP segments or UDP datagrams.
9. TCP and UDP data is put into IP packets for delivery.
© P.C. Wong Transparency No.2-3
Outline
1. What is Internet?
2. How is Internet connected?
3. How to send data on the Internet?
4. How are Internet applications supported?
© P.C. Wong Transparency No.2-4
Net 1Net 1Net 2Net 2
Net 3Net 3
What is Internet?
Servers
Inter-Net – An interconnected network of networks
© P.C. Wong Transparency No.2-5
Net 1Net 1Net 2Net 2
Net 3Net 3
World-wide-web (www)
An Overlay Network of Linked Web Documents
http://www.ie.cuhk.edu.hk
© P.C. Wong Transparency No.2-6
.COM – commercial
.NET - network
.GOV – government
.EDU – education
.ORG - organisation
.MIL - military
.BIZ - business
.INFO - information
.hk - hong kong
.cn - china
.tw – taiwanWhat about go.to?
www.hkcampus.netwww.hkedcity.net
www.hkcampus.netwww.hkedcity.net
Internet Domains
http://www.networksolutions.com
http://www.hkdnr.net.hk
Top domains
Hong Kong domains
© P.C. Wong Transparency No.2-7
Internet – the largest Wide Area Network
Internet: A worldwide network of networks
1. Initiated by Defense Advanced Research Projects Agency
ARPANET, later developed into the NSFnet
2. Connecting [Jul 2002] 162,128,493 hosts all over the world The number still doubles every two year.
Each host has a unique IP address.
3. The protocol suite - TCP/IP (1973-4)
4. Basic services - EMAIL, FTP, TELNET (1970)
5. Popular applications - Web (1990), Video Streaming via RTSP(1998),
Video Conferencing via H.323, and Voice over IP.
© P.C. Wong Transparency No.2-8
“Cool” internet appliances
World’s smallest web serverhttp://www-ccs.cs.umass.edu/~shri/iPic.html
IP picture framehttp://www.ceiva.com/
Web-enabled toaster+weather forecaster
© P.C. Wong Transparency No.2-9
Source: Computer Industry Almanac IncSource: Computer Industry Almanac Inc
Internet Connectivity
Million of Hosts
39
151
319
717
0
100
200
300
400
500
600
700
800
1995 1998 2000 2005
300 million
© P.C. Wong Transparency No.2-10
What’s the Internet: “nuts and bolts” view
1. millions of connected computing devices: hosts, end-systems
a. PCs workstations, servers
b. PDAs phones, toasters
running network apps
2. communication links
a. fiber, copper, radio, satellite
b. transmission rate = bandwidth
3. routers: forward packets (chunks of data)
local ISP
companynetwork
regional ISP
router workstation
servermobile
© P.C. Wong Transparency No.2-11
What’s the Internet: “nuts and bolts” view
1. protocols control sending, receiving of msgs
a. e.g., TCP, IP, HTTP, FTP, PPP
2. Internet: “network of networks”
a. loosely hierarchical
b. public Internet versus private intranet
3. Internet standards
a. RFC: Request for comments
b. IETF: Internet Engineering Task Force
local ISP
companynetwork
regional ISP
router workstation
servermobile
© P.C. Wong Transparency No.2-12
What’s a protocol?
human protocols:
1. “what’s the time?”
2. “I have a question”
3. introductions
… specific msgs sent
… specific actions taken when msgs received, or other events
network protocols:
1. machines rather than humans
2. all communication activity in Internet governed by protocols
Protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt
© P.C. Wong Transparency No.2-13
What’s a protocol?
a human protocol and a computer network protocol:
Hi
Hi
Got thetime?
2:00
TCP connection reqTCP connectionresponseGet http://www.awl.com/kurose-ross
<file>time
© P.C. Wong Transparency No.2-14
What do we do with the Internet?
Servers
Web Browsing
Instant Messaging
File Transfer
© P.C. Wong Transparency No.2-15
Many more applications!
Peer-to-peer applications Napster, Gnutella, Kazaa file exchange Searching for ExtraTerrestrial Intelligence (SETI)
Audio & video streaming Network games On-line purchasing Text messaging in PDAs, cell phones (SMS) Voice-over-Internet Online databases eServices, eLearning, Telemedicine, etc.
© P.C. Wong Transparency No.2-16
Who defines the Internet?
1. Internet Engineering Task Force (IETF)
a. Develops and reviews specifications intended as Internet standards.
2. Role of Standards
a. Allows interoperability
b. Allows smaller companies to enter large markets
c. Results in increase rate of innovation and evolution of technology and standards
3. Request for Comment (RFC)
a. A formal Internet document concerning an Internet issue
b. State: maturity level of an RFC
c. Status: requirement level of an RFC
http://www.ietf.org
© P.C. Wong Transparency No.2-17
Standardization Process
© P.C. Wong Transparency No.1-18
How to connect to the Internet?How to connect to the Internet?
© P.C. Wong Transparency No.2-19
Net 1Net 1Net 2Net 2
ISPISP
Internet Connectivity
撥號上網 (Dial-up Access)
專線上網 (Leased Line Access)
寬頻上網 (Broadband Access)
router
ADSL ModemCable ModemEthernet Connection
© P.C. Wong Transparency No.2-20
Media and Cabling – How to connect to a network?
1. Cable – allows you to connect devices
2. Connector – standard interfacefor making connections.
Note: We need different cables & connectorsfor different links.
© P.C. Wong Transparency No.2-21
What if the distance is too long?
1. Repeater
2. Hub – multiple port repeater
<100m<100m
Signal regenerationSignal regeneration
<100m<100m<100m<100m
<100m<100m<100m<100m
The signal is regenerated on all segments
uplinkuplink
© P.C. Wong Transparency No.2-22
Switches and Hub
Number of ports: 8/16/24/…
Nature: Hub or Switch (access/core)
Speed: 10/100/1Gbps
Interfaces: Fiber/Copper
Backplane bus: stackability
Uplink: connecting to core switch
Management: SNMP and web
Others:
redundant supply
control console
…
© P.C. Wong Transparency No.2-23
Ethernet Transmissions• The address of a node as defined by its LAN.
• The address in included in an Ethernet frame of data.
•Ethernet uses a six-byte physical address which is imprinted on the network interface card (NIC)
Transmission with a LAN
© P.C. Wong Transparency No.2-24
How can IP packet be sent on a local area network?
Data is divided into frames.
64-1518 bytes
Src address: 6 bytes
Dst address: 6 bytes
© P.C. Wong Transparency No.1-25
How to send data on the Internet?How to send data on the Internet?
© P.C. Wong Transparency No.2-26
IGS1.IE.CUHK.HK
adnetpc0
137.189.96.37
137.152.96.253
137.152.96.254
137.154.96.250
137.148.96.252
AGS.PWH.HK
IGS2.STH.HK137.150.96.252
137.189.96.131
T-1
137.189.96.252
137.154.96.251
137.148.96.47
137.150.96.48
magnet2.pwh.hk
magnet3.sth.hk
adnet1
Internet Addresses and Domains
Ethernet addressing cannot be used across networks.
© P.C. Wong Transparency No.2-27
IP Addressing
The Internet (IP) addressing. Each address is represented by4 bytes, denoting(1) Network address(2) Host address
1100101011001010 0010110100101101 1011011110110111 0000000100000001
202.45.183.1
Network-ID Host-ID
Host address=0 the network, Host address=1s broadcast.
© P.C. Wong Transparency No.2-28
Internet Addresses
1 1 1 1 Reserved for future use0
1 1 1 0 Multicast address
1 1 0 netid hostid
1 0 netid hostid
0 netid hostid
Class
A
B
C
D
E
24 bits (16777214)7 bits
14 bits 16 bits (65534)
21 bits 8 bits (254)
CUHK : 137.189.X.X (dotted decimal notation) -> a Class B network
1st Octet netid hostidA 1 - 126 p q.r.sB 128 - 192 p.q r.sC 192 - 223 p.q.r s
© P.C. Wong Transparency No.2-29
Subnet Addressing
1100101011001010 1100101011001010 1100101011001010 0111111101111111
IP Address: 202.45.183.127
Subnet Mask: 255.255.255.240
1111111111111111 1111111111111111 1111111111111111 1111000011110000
Result subnet ID: 202.45.183.112
1100101011001010 1100101011001010 1100101011001010 0111000001110000
Subnet range202.45.183.112-1270000 – net ID, 1111 - broadcast
© P.C. Wong Transparency No.2-30
Packet delivery on the Internet - Switching and Routing
1. Data is divided into small packets (IP packets)
2. Switching
a. Each packet is examined by a switch/router and forwarded to an output link.
3. Routing
a. The packet is targeted to the destination based on a certain routing path.
© P.C. Wong Transparency No.2-31
IP Packet Format
PADDING
SOURCE IP ADDRESS
DESTINATION IP ADDRESS
IP OPTIONS (IF ANY)
FRAGMENT OFFSET
TOTAL LENGTH
IDENTIFICATION
0 8 1631
HLENVERS SERVICE TYPE
FLAGS
HEADER CHECKSUMPROTOCOLTIME TO LIVE
DATA
...
VERS: versionHLEN: header length (32-bit words) TOTAL LENGTH: packet size (octets)
PacketHeader
PacketData
© P.C. Wong Transparency No.2-32
How are IP packets routed in a network?
magnet2.pwh.hk
IGS1.IE.CUHK.HK
137.152.96.253
137.152.96.254
137.154.96.250
137.148.96.252
AGS.PWH.HK
IGS2.STH.HK137.150.96.252
137.189.97.37
T-1
137.189.96.252
137.154.96.251
137.148.96.47
137.150.96.48
magnet3.sth.hk
adnetpc0
(1)
(2)
(3)
(4)
Issues1. Direct delivery vs. indirect delivery
2. Gateway selection
3. Routing table
4. Default routes
5. Host-Specific routes
IP addresswith net_id routing137.152.0.0 directly137.154.0.0 directly137.148.0.0 directly137.150.0.0 137.154.96.250137.189.0.0 137.152.96.254
The Routing table for AGS.PWH.HK
© P.C. Wong Transparency No.1-33
How are Internet applications supported?How are Internet applications supported?
© P.C. Wong Transparency No.2-34
TCP and UDP?
TCP/IP : (Transmission Control Protocol/Internet Protocol) It is a set of protocols developed and used in the ARPANET, supported by the Defense Advanced Projects Research Agency (DARPA).
It supports two major servicesa. Connectionless packet delivery service (UDP)b. Reliable Stream Transport service (TCP)
It featuresa. Network technology independenceb. Universal interconnectionc. End-to-end acknowledgmentsd. Application protocol standards
Its major applicationsa. e-mail (SMTP)b. file transfer (FTP)c. remote login (TELNET)d. web (HTTP)
physicalnetwork
router orgateway
© P.C. Wong Transparency No.2-35
TCP/IP Protocols and Applications
TCP - Transmission Control ProtocolUDP - User Packet ProtocolICMP - Internet Control Message ProtocolIP - Internet ProtocolARP - Address Resolution ProtocolRARP - Reverse ARPSLIP - Serial Line Interface ProtocolPPP - Point-to-point Protocol
IP
Ethernet, FDDI,ATM, etc.
ARP, RARP
ICMP TCP UDP
PPP, SLIP
ApplicationApplication Application
ports
FTP, TELNET, MAIL, Other Applications
© P.C. Wong Transparency No.2-36
Relationship of layers and addresses in TCP/IP
Identify a LAN station
Identify a Internet host
Identify an Internet application
© P.C. Wong Transparency No.2-37
TCP Port numbers
Decimal Keyword Description015791113202123253742537980103104113117119139
--TCPMUXRJEECHODISCARDUSERSDAYTIMEFTP-DATAFTPTELNETSMTPTIMENAMESERVERDOMAINFINGERHTTPX400X400SNDAUTHUUCP-PATHNNTPNETBIOS-SSN
ReservedTCP multiplexerRemote job entryEchoDiscardActive usersDaytimeFile transfer protocol-dataFile transfer protocolTerminal connectionSimple mail transfer protocolTimeHost name serverDomain name serverFingerWeb serverX.400 Mail ServiceX.400 Mail SendingAuthentication ServiceUUCP Path ServiceUSENET news transfer protocolNETBIOS session service
© P.C. Wong Transparency No.2-38
binding: 23-204
1048
TELNET client
23
TELNET Server
7 21
magnet1137.189.96.31
iestp10137.189.96.210
204
TELNET Client
9 208
How can a server support multiple clients?
TCP assigns some well-known ports for communications- server port defines the application.- client port defines the client.
Solution: Connection is identified by a pair of end-points
E.g., (137.189.96.31, 23) and (137.189.96,210, 204)
© P.C. Wong Transparency No.2-39
Protocol Layering
Application
Transport
Internet
Interface
Internet
Interface
Physicalnetwork 1
Physicalnetwork 1
Application
Transport
Internet
Interface
Gateway G
frame
packet
datagram or transport segment
Frame Data AreaFrame Header
Packet Header Packet Data Area
Header Transport data
Kernal
User
H/W
© P.C. Wong Transparency No.2-40
Internet Connection via TCP
© P.C. Wong Transparency No.2-41
FTP: File Transfer Protocol
userinterface
user protocol
interpreter
user data transfer
function
serverprotocol
interpreter
serverdata transfer
functionfile systemfile system
user at aterminal
ServerClient
controlconnection
dataconnection
21
20
Commands 3 or 4 bytes NVT ASCII w/wo arguments
Replies 3-digit numbers, optional messages ASCII
© P.C. Wong Transparency No.2-42
FTP commands (NVT ASCII)
ABOR
LIST filelist
PASS password
PORT n1,n2,n3,...,n6
QUIT
RETR filename
STOR filename
SYST
TYPE type
USER username
abort previous FTP command and any data transfer
list files or directory
password on server
client IP address (n1..n4) and port (n5x256+n6)
logoff from server
retrieve (get) a file
store (put) a file
server returns system type
specify file type:A (for ascii) I (for image)
username on server
Name Meaning
© P.C. Wong Transparency No.2-43
FTP commands and replies
/data/staff/pcwong> ftp -d magnet1Connected to magnet1.220 magnet1 FTP server (SunOS 4.1) ready.Name (magnet1:pcwong): pcwong---> USER pcwong331 Password required for pcwong.Password:---> PASS rachel41230 User pcwong logged in.ftp> dir cantoni.1---> PORT 137,189,96,21,11,33200 PORT command successful.---> LIST cantoni.1150 ASCII data connection for /bin/ls (137.189.96.21,2849) (0 bytes).-rw-r--r-- 1 pcwong staff 1953 Nov 10 18:16 cantoni.1226 ASCII Transfer complete. �remote: cantoni.165 bytes received in 0.11 seconds (0.56 Kbytes/s)ftp> get cantoni.1---> PORT 137,189,96,21,11,34200 PORT command successful.---> RETR cantoni.1150 ASCII data connection for cantoni.1 (137.189.96.21,2850) (1953 bytes).226 ASCII Transfer complete.local: cantoni.1 remote: cantoni.12009 bytes received in 0.051 seconds (39 Kbytes/s)
© P.C. Wong Transparency No.2-44
1. User clicks on http://www.singtao.com/
2. Ethereal network analyzer captures all frames observed by its Ethernet NIC
3. Sequence of frames and contents of frame can be examined in detail down to individual bytes
How do protocols work together?
Internet
http://www.ethereal.com/http://www.ethereal.com/
© P.C. Wong Transparency No.2-45
Top Pane shows
frame/packet sequence
Middle Pane shows encapsulation for a
given frame
Bottom Pane shows hex & text
© P.C. Wong Transparency No.2-46
What do you need to know?
1. Internet – a network of networks.
2. Protocol – data format, procedures for communications.
3. Internet hosts have domain names and IP addresses.
4. IP address – 4 byte represented by (n.n.n.n)
5. Information is carried by IP packets up to 64 Kbytes each.
6. IP packets are routed independently to the destination (packet switching) based on the IP address on the packet.
7. There are two common transport protocols – TCP and UDP.
a. TCP – connection oriented.
b. UDP – connectionless (datagram)
8. Applications (e.g., FTP) are run on top of TCP or UDP. Application data is put into TCP segments or UDP datagrams.
9. TCP and UDP data is put into IP packets for delivery.
© P.C. Wong Transparency No.1-47
Thank YouThank You