1-intro.ppt 221KB Jun 23 2011 10:19:06 AM

(1)

Introduction to Computer Network 1

Computer Networks

Ilam University

(2)

Introduction to Comp uter Network

2

Outline

 Agenda

 Policy, Grading, reading materials, etc.  Communication.

(3)

3

Course Materials

 Course Web page

 visit regularly

 Textbook

 “Computer Networks, A system approach”. Peterson & Davie

4th edition



صن تاراشتنا ،نایکلم ناسحا ،تنرتنیا یسدنهم

 Grading

 Midterm 35%  Final 55%

 homework 10%

(4)

4

Prerequisition

 General knowledge in Computer.

 Fluency in English, specially reading.

 C++ programming.

 Knowledge of UNIX (LINUX) system and

(5)

5

Communication as need.

 Base of community

 Collection of trees is not a community.

 Transferring data, knowledge, experience among people

 Base of civilization.  Psycological need.

 Love, affection.  Just talking.

(6)

6

Primary Communication means

 Language

 Conventions

 Body Language,

 Meta language.

 Universal.

 Problems:

 Limited in Time and space.

 We are struggling all the history to overcome

(7)

7

Communication elements

 Producer, Sender

 Speaker

 Consumer, Receiver

 Listener

 They both do processing and have limitation

 Message - Talk

 Transfer media, like air

 Substance

 Capacity

(8)

8

Type of communication

 One to one

 Direct talk.

 One to many

 Talks, conferencing

 Many to Many

 Like mass media, newspaper.

 Domain of communication

 Small, primary society

 Medium, more developed society.

(9)

9

First Step- Writing

 One of the most important human being

invention. (Why?)

 Overcome the primary limitations.

 Time: By writing it down.

 Space: Distributing more copies, library, post, etc.

 Problems:

 Indirect Communication, Through paper.

 Slow in producing and consuming

 Need proficiency

(10)

10

Next Step- Mailing

 Distribute messages as fast as and as far as

possible.

 Overcome mostly space limitation, while widen

the domain of communication.

 Media- human being network system.

 Indirect communication.

 Encoded message

(11)

11

New wave- Telegraph

 In 1837, Samuel B. Morse invented it.

 Text message is encoded by dot and dashed

(binary, digital system).

 Message switching, human coding for efficiency,

and hop by hop routing.

 Fast transmission, (Time limitation)

 Slow production (25-30 word/min)

(12)

12

Telephone

 In 1876, While working on multiplexing

telegraph, invented By A. Graham Bell.

 One to one, completely real time

communication.

 No need to proficiency.

 Fast, (time limitation)

 Easy to use or produce data.

 Exponential growths, 1000 in 1877 to 50,000 in

(13)

13

Broadcast media

 Printing, newspapers,

 Easy to reproduce the same data.  Easy to distribute message.

 Slow in producing and contribution.  Radio

 Easy to distribute message.

 Fast in producing and contribution of message.  Limited of type of message, only voice.

 TV

(14)

14

Computer Network

 Fast in producing, processing, distributing

and consuming messages.

 No limitation in time and space.

 Support different type of communication.

 Mass media, news group.

 One to many, mailing list.

 One to one, mail, chat, talk.

 Support of different type of message, data

(15)

15

History of the Internet

 70’s: started as a research project, 56 kbps, < 100 computers

 80-83: ARPANET and MILNET split,

 85-86: NSF builds NSFNET as backbone, links 6

Supercomputer centers, 1.5 Mbps, 10,000 computers

 87-90: link regional networks, NSI (NASA), ESNet(DOE), DARTnet, TWBNet (DARPA), 100,000 computers

 90-92: NSFNET moves to 45 Mbps, 16 mid-level networks

 94: NSF backbone dismantled, multiple private backbones

(16)

16

Growth of the Internet

Number of Hosts on the Internet:

Aug. 1981 213 Oct. 1984 1,024 Dec. 1987 28,174 Oct. 1990 313,000 Oct. 1993 2,056,000 Apr. 1995 5,706,000 Jul. 1997 19,540,000 Jul. 1999 59,249,900 Jul. 2001 117,288,000

(17)

17

(18)

18

Services Provided by the

Internet

 Shared access to computing resources

 telnet (1970’s)

 Shared access to data/files

 FTP, NFS, AFS (1980’s)

 Communication medium over which people interact

 email (1980’s), on-line chat rooms, instant messaging (1990’s)  audio, video (1990’s)

 replacing telephone network?

 A medium for information dissemination

 USENET (1980’s)  WWW (1990’s)

 replacing newspaper, magazine?

 audio, video (1990’s)

(19)

19

Today’s Vision

Everything is digital: voice, video, music,

pictures, live events

Everything is on-line: bank statement,

medical record, books, airline schedule, weather, highway traffic, toaster,

refrigerator …

Everyone is connected: doctor, teacher,

(20)

20

Today’s Vision

 Electronic commerce

 virtual enterprise

 Internet entertainment

 interactive sitcom

 World as a small village

 community organized according to interests

 enhanced understanding among diverse groups

 Electronic democracy

 little people can voice their opinions to the whole world

 little people can coordinate their actions

 bridge the gap between information haves and have-not’s

 Electronic terrorism

(21)

21

Industrial Players

 Telephone companies

 own long-haul and access communication links, customers

 Cable companies

 own access links

 Wireless/Satellite companies

 alternative communication links

 Utility companies: power, water, railway

 own right of way to lay down more wires

 Medium companies

 own content

 Internet Service Providers

 Equipment companies

 switches/routers, chips, optics, computers

(22)

22

What is Next?

 Who knows?!!

 Use your imagination

 If you can predict something here you will be

a winner

 Peer to peer

 Ebay

 Google

(23)

23

Commercial Internet after

1994

NSF Network Regional ISP

America On Line

IBM Bartnet

Campus Network Joe's Company

Stanford

Xerox Parc Berkeley

NSF Network

Internet MCI UUnet

SprintNet

Modem

(24)

24

Backbone

ISP ISP

Internet Physical

Infrastructure

 Residential

Access

 Modem

 DSL

 Cable modem  Satellite

 Enterprise/ISP access,

Backbone transmission

 T1/T3, DS-1 DS-3

 OC-3, OC-12

 ATM vs. SONET, vs. WDM

 Campus network

 Ethernet, ATM

 Internet Service Providers

 access, regional, backbone

 Point of Presence (POP)