Introduction to Computer Network 1

Computer Networks

Ilam University

Dr. Mozafar Bag-Mohammadi

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

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Course Materials Course Web page

visit regularly Textbook

“Computer Networks, A system approach”. Peterson & Davie 4th edition

مهندسی اینترنت، احسان ملکیان، انتشارات نص Grading

Midterm 35% Final 50% homework 10% 5( قرآن قبل از امتحان پایان ترم 30حفظ یک حزب )غیر از جزء %

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Prerequisition

General knowledge in Computer. Fluency in English, specially reading. C++ programming. Knowledge of UNIX (LINUX) system and

programming.

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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. Releasing someone. Base of Culture.

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Primary Communication means Language

Conventions Body Language,

Meta language. Universal.

Problems: Limited in Time and space. We are struggling all the history to overcome

these limitation.

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Communication elements Producer, Sender

Speaker Consumer, Receiver

Listener

They both do processing and have limitation Message - Talk Transfer media, like air

Substance Capacity Delay

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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. Large, more advance society.

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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 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, 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 All like radio, but with richer 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 2.4 Gbps, 200 millions computers

in 150 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 1999

Data 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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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 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 Medium companies

own content Internet Service Providers Equipment companies

switches/routers, chips, optics, computers Software companies

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What is Next?

Who knows?!! Use your imagination If you can predict something here you will be

a winner Peer to peer Ebay Google weblogs

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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)