Networks and the Internet

Topic 3

Three Important Networking Technologies

Networks, Internet, WWW

A Modem

Networks, Internet, WWW

0 0 1 1 1 0 1 M M 0 0 1 1 1 0 1

Data communications

Sending messages/information between two or more computers.

File system

Printer

Server

Client Client

Client Client

Upstream Downstream

Data communications media

Implementation Example Speed

Multiplier Media

Dial Up Modem 56 kbps 1

Wireless S 500 kbps 10X S

Wireless 3G MT 1,500 kbps 30X MT

DSL 1+ Mbps 20X TP

Cable Modem 2+ Mbps 40X C

Ethernet LAN 10 - 100 Mbps 200X – 2,000X TP, C, F

T1, T2, T3 TP, C, F

OC-192 10,000 Mpbs 200,000X F

Example Connections & Service

Notes:TP=Twisted Pair, C=Coaxial Cable, F=Fiber, S=Satellite, MT=Microwave Towers/cellularT1, T2, T3 are dedicated lines from Org to ISP or ISP to InternetOC Internet backbone lines

http://mindprod.com/jgloss/transmissionspeed.html

http://indianblogger.com/understanding-the-generations-1g-2g-3g-and-4g/

Data Communication

• Network: two or more computers or devices linked by communication lines.– Each computer/device is a node– Transmitter and receiver are nodes

• The network is the medium• Communication rules are defined by a protocol

Data Communication

Networks, Internet, WWW – 5 of 22

• Communication protocol– An agreed-upon format or procedure for

transmitting data.– Implemented in hardware and/or software

• Key issues– Deliver message efficiently– Detect errors– Correct errors

Messages and Packets

Packet A1 Packet A2 Packet A3

Message ATrailer Body Header

A Packet

Flow Label (20 bits)Marks a packet as part of a specific flow

Payload Length (16 bits)

Next Header(8 bits)

Name of nextheader

Source IP Address (128 bits)

Diff-Serv(8 bits)

Version(4 bits)

Hop Limit(8 bits)

Destination IP Address (128 bits)

Next Header or Payload (Data Field)

Routers

Router 4Router 2

Router 1

Router 4

Internet

Routers

Router 3

Router 4

Router 6

Router 7 Router 9

Router 8Router 1

Router 2

Router 4 Router 5

Router 5Router 5

Sending Messages Across a Network

Packet A1 Packet A2 Packet A3

Message A

Packet A1 Packet A2 Packet A3

Message A

Packet A3 Packet Packet

Packet Packet A2 Packet

Open Packet Packet

Packet A1 Packet Open

Packet Packet Open

Packet Packet Packet

U.S. Internet Backbone

Networks, Internet, WWW – 1 of 20

LANs and WANs

• LAN (local area network)– A network that connects systems within a limited

physical area (department, dorm).• WAN (wide area network)

– A network that connects systems throughout a large geographic area (entire business, university/branches).

A LAN

File system

Printer

Server

Client Client

Client Client

A WAN

Internetworking

• Process of linking two or more networks. Server

Bridge

Gateway

Server

WorkstationWorkstation

Workstation

Server

WorkstationWorkstation

Workstation

WorkstationWorkstation

Workstation Workstation

A bridge links similar networks

A gateway links dissimilar networks

Router and a Switch

Internet Addressing

sbaserver1.sba.muohio.edu

Server within SBA sub-domain

SBA sub-domain

Miami University domain

Top-level domain

Internet Addressing

• Physical transmission requires IP address

• Domain name system converts domain name to equivalent IP address

sbaserver1.sba.muohio.edu 134.53.40.2

Internet Addressing

http://www.whatismyip.com/http://www.visualware.com/

Internet Addressing

TCP/IP

Summary: TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN. The IP component provides routing from the department to the enterprise network, then to regional networks, and finally to the global Internet. On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP to be robust and automatically recover from any node or phone line failure. This design allows the construction of very large networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed and uncorrected for long periods of time. As with all other communications protocol, TCP/IP is composed of layers:

•IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world. •TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received. •Sockets - is a name given to the package of subroutines that provide access to TCP/IP on most systems.

TCP/IP

TCP is a connection-oriented transport protocol that sends data as an unstructured stream of bytes. By using sequence numbers and acknowledgment messages, TCP can provide a sending node with delivery information about packets transmitted to a destination node. Where data has been lost in transit from source to destination, TCP can retransmit the data until either a timeout condition is reached or until successful delivery has been achieved. TCP can also recognize duplicate messages and will discard them appropriately. If the sending computer is transmitting too fast for the receiving computer, TCP can employ flow control mechanisms to slow data transfer. TCP can also communicate delivery information to the upper-layer protocols and applications it supports.