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An Introduction to Computer Networks

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In 1837, Samuel B. Morse invented it. ... NSI (NASA), ESNet(DOE), DARTnet, TWBNet (DARPA) ... Everything is digital: voice, video, music, pictures, live events ... – PowerPoint PPT presentation

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Title: An Introduction to Computer Networks


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

2
Outline
  • Agenda
  • Policy, Grading, reading materials, etc.
  • Communication.
  • Overview and history of the Internet

3
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.

4
Course Materials
  • Course Web page
  • http//ece.ut.ac.ir/classpages/Networks/
  • visit regularly
  • Textbook
  • Computer Networks, A system approach. Peterson
    Davie 3rd edition

5
Grading
  • Homework assignments, around 30
  • 4-5 five homework and a small project.
  • Severe late penalties!
  • Midterm exam around 35.
  • Final exam around 35.

6
Prerequisition
  • General knowledge in Computer engineering.
  • C programming.
  • Knowledge of UNIX (LINUX) system and programming.
  • Fluency in English, specially reading.

7
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.

8
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.

9
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)

10
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.

11
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

12
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.

13
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.

14
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

15
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.

16
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.

17
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

18
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/
19
Recent Growth (1991-2000)
20
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?

21
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

22
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

23
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

24
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

25
Industrial Players
  • Medium companies
  • own content
  • Internet Service Providers
  • Equipment companies
  • switches/routers, chips, optics, computers
  • Software companies

26
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
27
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)

28
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