Transcript Introduction

An Introduction
to
Computer Networks
Lecture 1: Introduction
University of Tehran
Dept. of EE and Computer Engineering
By:
Dr. Nasser Yazdani
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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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Grading
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Homework assignments, around %30
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4-5 five homework and a small project.
Severe late penalties!
Midterm exam around %35.
Final exam around %35.
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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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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
Small, primary society
 Medium, more developed society.
 Univ.
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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1000000000
100000000
10000000
1000000
100000
10000
1000
100
10
1
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
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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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Backbone
Residential Enterprise/ISP
Access
access, Backbone
 Modem
transmission
 DSL
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Cable
modem
Satellite
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ISP
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Campus network
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Ethernet, ATM
Internet Service
Providers
T1/T3, DS-1 DS-3
OC-3, OC-12
 access, regional,
ATM vs. SONET, vs.
backbone
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WDM
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