1

Introduction

Computer Networks

2

Motivation and Scope

Computer networks and internets: an overview of concepts, terminology

and technologies that form the basis for digital communication in private corporate networks the the global

Internet.

3

Motivation for Networks

Information AccessSharing of ResourcesFacilitate Communications

4

What a Network Includes

Transmission hardwareSpecial-purpose hardware devices

interconnect transmission mediacontrol transmissionrun protocol software

Protocol softwareencodes and formats datadetects and corrects problems

5

What a Network Does

Provides communication that isReliableFairEfficientFrom one application to another

6

What a Network Does [continued]

Automatically detects and correctsData corruptionData lossDuplicationOut-of-order delivery

Automatically finds optimal path from source to destination

7

Data Communication versus Networking

With only two nodes, mostly EE issues.

With more than two nodes, lot more issues!

8

Direction of Transmission

Point to Point Broadcast

9

Network Topologies

10

Transmission Media

WirelineStringGarden HoseCopper

Twisted PairCoax

Optical Fiber

WirelessSoundLight and mirrorsInfraredRFMicrowave

11

Network Scope

Local Area Network (LAN)Metropolitan Area Network (MAN)Wide Area Network (WAN)

12

Data Transmission

Serial

Parallel

13

Multiplexing

14

Communication Modes

SimplexHalf-duplexFull-duplex

15

Connection-oriented versus Connectionless

Connection SetupData TransferConnection

Termination

Data Transfer

16

Circuit Switching versus Packet Switching

Dedicatedfixed bandwidthroute fixed at setupidle capacity wastednetwork state

Best Effortend-to-end controlmultiplexing

techniquere-route capabilitycongestion problems

17

Examples

Public Switched Telephone NetworkInternetPostal ServiceTrainCar and highway system

18

Standards

HardwareSoftwareProtocolsAdvantages and DisadvantagesProprietary, De Facto, De JureStandards Bodies

IETF, IEEE, OSI, ANSI, ATM Forum, etc.

19

Protocols

Rules, standards and etiquetteMetric SystemEnglishDinner partyMorse CodeTCP/IPHTML

20

Layering

21

Headers, Data and Trailers

22

Encapsulation

23

ISO OSI Reference Model

7: Application Layer6: Presentation Layer5: Session Layer4: Transport Layer3: Network Layer2: Data link Layer1: Physical Layer

24

Interfaces and Services

PDUsSDUsSAPsPeer communicationsService Primitivesetc... read Tanenbaum 1.3.3 and 1.3.5

25

TCP/IP Model

5: Application Layer4: Transport Layer3: Network Layer2: Data link Layer1: Physical Layer

26

TCP/IP versus OSI

"Rough consensus and running code”SimplicityTime to marketAvailability

27

Network Classification

Physical medium: copper, fiber, wireless

Scope: LAN, MAN, WANTopology: bus, star, ring, meshSwitching style: circuit, packetApplication: voice, data, videoProtocol: IP, OSI, Ethernet, ATMTransmission rate: 10Mb/s, Gigabit

28

Terms I (we) Often Use

Frames: think data link layerPackets: think network layerDatagrams: think IPSegments: think TCPCells: think ATMLayer <x>: refer to reference models

29

The End-to-End Argument

"End-to-End Arguments in System Design”J.H. Saltzer, D.P. Reed, and D.D. Clarkhttp://web.mit.edu/Saltzer/www/

publications/