Introduction.ppt 1096KB Jun 23 2011 10:21:38 AM

An Introduction
to
Computer Networks
Lecture 1: Introduction
University of Tehran
Dept. of EE and Computer Engineering
By:
Dr. Nasser Yazdani
Univ. ov Tehran

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

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Agenda
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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
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Course Web page
http://ece.ut.ac.ir/classpages/Networks/
 visit regularly

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Textbook
“Computer Networks, A system approach”. Peterson &
Davie 3rd edition

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Other useful books
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A. Tanenbaum, Computer Networks
R. Stevens, TCP/IP Illustrated (vol 1)
S. Keshav, An Engineering Approach to Computer
Networking
Kurose and Ross, Computer Networking
Walrand, Communication Networks, 2nd Ed

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Grading
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Homework assignments, around %30
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3-4 five homework
A small project.
Severe late penalties!

Course involve programming on C/C++ in
Unix environment.
Few small quizs around %10
Midterm exam around %30.
Final exam around %30.
There is a %40 cut off on total exam points.
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Prerequisition
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General knowledge in Computer
engineering.
C programming.
Knowledge of UNIX (LINUX) system
and programming.
Fluency in English, specially
reading.
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How to survive this course

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Materials sound simple and easy, but
they are not.
Do not leave everything to the exam
night!.
Not copy the homework!, try them by
yourself.
You can read the course by yourself, but
the class makes the life for you easier.

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Some Ground Rules
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Let’s make this educational and enjoyable.
It’s a big class, I enjoy questions and ideas
from the class.

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Ask questions and raise points.
Identify yourself when you ask questions.
Listen to other people’s questions.
Be here.

Be here on time.

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Communication as a human
being need.
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Base of community
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Transferring data, knowledge,
experience among people
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Collection of trees is not a community.

Base of civilization.

Psycological need.
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Love, affection.
Just talking.
Releasing someone.
Base of Culture.

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Primary Communication
means
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Language
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Body Language,
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Conventions
Meta language.
Universal.

Problems:
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Limited in Time (delay) and space
(domain).
We are struggling all the history to
overcome these limitation.

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Communication elements
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Producer, Sender
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Consumer, Receiver
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Speaker (in conversation)
Listener
They both do have processing-limitation

Message- Talk
Transfer media, like air
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Substance
Capacity (very limited)
Delay (considerable)
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Type of communication
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One to one
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One to many
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Talks, conferencing

Many to Many
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Direct talk.

Like mass media, new paper.

Domain of communication
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Small, primary society
Medium, more developed society.
Large, more advance society.
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First Step- Writing
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One of the most important human being
invention. (Why?)
Overcome the primary limitations.
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Time: By writing it down.
Space: Distributing more copies, library, post, etc.

Problems:
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Indirect Communication, Through paper.
Slow in producing and consuming
Need proficiency
Encoding message
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Next Step- Mailing
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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
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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
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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
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Printing, news papers,
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Radio
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Easy to reproduce the same data.
Easy to distribute message.
Slow in producing and contribution.
Easy to distribute message.
Fast in producing and contribution of message.
Limited of type of message, only voice.

TV
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All like radio, but with reach data.
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Computer Network
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Fast in producing, processing, distributing
and consuming messages.
No limitation in time and space.
Support different type of communication.
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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
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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
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

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Data available at: http://www.netsizer.com/

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Recent Growth (19912000)

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Recent Growth (by 2004)

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

Services Provided by the
Internet

Shared access to computing resources
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Shared access to data/files
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telnet (1970’s)
FTP, NFS, AFS (1980’s)

Communication medium over which people interact
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email (1980’s), on-line chat rooms, instant messaging (1990’s)
audio, video (1990’s)
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replacing telephone network?

A medium for information dissemination
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USENET (1980’s)
WWW (1990’s)
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replacing newspaper, magazine?

audio, video (1990’s)
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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?
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Electronic commerce
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Internet entertainment
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virtual enterprise
interactive sitcom

World as a small village
community organized according to
interests
 enhanced understanding among
diverse groups
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What is Next?
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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
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Electronic terrorism
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hacker can bring the whole world to
its knee

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Industrial Players
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Telephone companies
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Cable companies
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own access links

Wireless/Satellite companies
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own long-haul and access
communication links, customers

alternative communication links

Utility companies: power, water,
railway
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own right of way to lay down more
wires

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Industrial Players
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Medium companies
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own content

Internet Service Providers
 Equipment companies
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switches/routers, chips, optics,
computers

Software companies

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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

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Residential
Access
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Modem
DSL
Cable
modem
Satellite

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Backbone

ISP

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

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

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Homework 0
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Install Linux on your computer
Try to be professional on Unix if you
are not so.
For Communication Engineer: Learn
C/C++ programming well on Unix
environment.
Your first assignment will come
soon!.
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Next Lecture
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Computer network foundation.
Read Chapter 1

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