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

Computer Networks
Ilam University
Dr. Mozafar Bag-Mohammadi

Introduction to Computer Network

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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




Textbook




visit regularly
“Computer Networks, A system approach”. Peterson & Davie
4th edition
‫ انتشارات نص‬،‫ احسان ملکیان‬،‫ مهندسی اینترنت‬

Grading





Midterm 35%
Final 55%
homework 10%

‫پر کردن فرم عدم تقلب در تمرینات‬

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

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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
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

Consumer, Receiver






Speaker
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




One to many




Talks, conferencing

Many to Many




Direct talk.

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
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
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




Shared access to data/files




telnet (1970’s)
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

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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
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

Internet entertainment
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community organized according to interests
enhanced understanding among diverse groups

Electronic democracy






interactive sitcom

World as a small village
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

virtual enterprise

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
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

Cable companies
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



own content

Internet Service Providers
Equipment companies




own right of way to lay down more wires

Medium companies




alternative communication links

Utility companies: power, water, railway




own access links

Wireless/Satellite companies




own long-haul and access communication links, customers

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
Joe's Company
Campus Network

Berkeley

Stanford
Regional ISP

Bartnet
Xerox Parc

SprintNet
America On Line

UUnet
NSF Network
IBM
NSF Network

Modem

Internet MCI
IBM

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Internet Physical
Infrastructure
ISP



Residential
Access



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Modem
DSL
Cable
modem
Satellite



Backbone

Enterprise/ISP access,
Backbone transmission


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T1/T3, DS-1 DS-3
OC-3, OC-12
ATM vs. SONET, vs.
WDM

ISP



Campus network




Ethernet, ATM

Internet Service Providers
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


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access, regional, backbone
Point of Presence (POP)
Network Access Point (NAP)

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