univ. ov tehranintroduction to computer network1 computer networks an introduction to computer...

Univ. ov Tehran Introduction to Computer Network

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An Introduction to

Computer NetworksComputer Networks

University of TehranDept. of EE and Computer Engineering

By:Dr. Nasser Yazdani

Lecture 1: Introduction


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OutlineOutline Agenda Policy, Grading, reading materials, etc. Communication. Overview and history of the Internet


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Agenda To establish a base for future computer

network work and study. Review networking technologies, protocols. Finally, prepare to perform some projects

in computer networks which are essential in national development, designing and building switches, routers, etc.


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Course Materials Course Web page

http://ece.ut.ac.ir/classpages/Networks/ visit regularly

Textbook“Computer Networks, A system approach”.

Peterson & Davie 3rd edition


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Grading Homework assignments, around %30

4-5 five homework and a small project. Severe late penalties!

Midterm exam around %35. Final exam around %35.


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Prerequisition

General knowledge in Computer engineering.

C programming. Knowledge of UNIX (LINUX) system

and programming. Fluency in English, specially

reading.


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Communication as a human being 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. Releasing someone. Base of Culture.


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Primary Communication means

Language Conventions

Body Language, Meta language. Universal.

Problems: Limited in Time (delay) and space

(domain). We are struggling all the history to

overcome these limitation.


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Communication elements Producer, Sender

Speaker (in conversation) Consumer, Receiver

Listener They both do have processing-limitation

Message- Talk Transfer media, like air

Substance Capacity (very limited) Delay (considerable)


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Type of communication One to one

Direct talk. One to many

Talks, conferencing Many to Many

Like mass media, new paper. Domain of communication

Small, primary society Medium, more developed society. Large, more advance society.


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First Step- WritingFirst 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 Encoding message


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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 Slow.


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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) The daily Telegraph.


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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 1880


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Broadcast media Printing, news papers,

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 All like radio, but with reach data.


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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 Only problem, need proficiency.


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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 Today: backbones run at 10 Gbps, around160 millions

computers in 160 countries


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Growth of the Internet

Number of Hosts on the Internet:

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

1

10

100

1000

10000

100000

1000000

10000000

100000000

1000000000

1981 1984 1987 1990 1993 1996 1999Data available at: http://www.netsizer.com/


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Recent Growth (1991-2000)


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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)

replacing radio, CD, TV?


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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, broker, mother, son, friends, enemies


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What is Next? Electronic commerce

virtual enterprise Internet entertainment

interactive sitcom World as a small village

community organized according to interests

enhanced understanding among diverse groups


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What is Next? 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 hacker can bring the whole world to

its knee


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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


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Industrial Players

Medium companies own content

Internet Service Providers Equipment companies

switches/routers, chips, optics, computers

Software companies


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Commercial Internet after 1994

NSF Network

Regional ISP

America On Line

IBM

BartnetCampus Network

Joe's CompanyStanford

Xerox Parc

Berkeley

NSF Network

Internet MCI

UUnet

SprintNet

Modem

IBM


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BackboneISP

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) Network Access Point

(NAP)


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