An Introduction to Computer Networks

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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

• 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- 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

• 70s started as a research project, 56 kbps, lt
  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

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 (1970s)
• Shared access to data/files
• FTP, NFS, AFS (1980s)
• Communication medium over which people interact
• email (1980s), on-line chat rooms, instant
  messaging (1990s)
• audio, video (1990s)
• replacing telephone network?
• A medium for information dissemination
• USENET (1980s)
• WWW (1990s)
• replacing newspaper, magazine?
• audio, video (1990s)
• replacing radio, CD, TV?

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Todays 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-nots
• 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
Joe's Company
Berkeley
Stanford
Regional ISP
Campus Network
Bartnet
Xerox Parc
SprintNet
America On Line
UUnet
NSF Network
IBM
NSF Network
Modem
Internet MCI
IBM
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Internet Physical Infrastructure
Backbone
ISP
ISP

• 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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