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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
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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
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Kurose and Ross, Computer Networking Univ.Walrand, Communication Networks, 2nd Ed ov Tehran Introduction to Computer Network 

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Grading
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Homework assignments, around %30
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4-5 five homework Late penalties!

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Course involve programming on C/C++ in Unix environment. Few small quizs around %10 Midterm exam around %30. Final exam around %30.

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Note: 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/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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Special Warning
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This is computer network course not queue theory!
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There are not much Mathematics (Attention for EE students!) There are programming in the course Still we think the course is not easy. Needs a lot of work.

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Indeed, It is in a higher level than just sending signals.
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Why Study Computer Network?
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To graduate!
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To get a degree To be engineer. It is good in the society, for prestige, marriage, etc.

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Networking is everything!
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It does not matter what you know. It is matter who you know.

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What you Learn?
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Insight: key concepts in networking
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Knowledge: how the Internet works
Internet architecture  IP protocol suite  Applications (Web, e-mail, P2P, …) Skill: network programming
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Protocols Layering Resource allocation Performance evaluation

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Socket programming Designing and implementing protocols
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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.

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Psycological need.
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Base of civilization.

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

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Problems:
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Meta language. Universal.

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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Speaker (in conversation) Listener They both do have processing-limitation

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Consumer, Receiver
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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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Direct talk.

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One to many
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Talks, conferencing
Like mass media, new paper.

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Many to Many
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Domain of communication
Small, primary society  Medium, more developed society.  Univ. ov Tehranmore advance to Computer Network Large, society. Introduction
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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. Indirect Communication, Through paper. Slow in producing and consuming Need proficiency Encoding message
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Problems:
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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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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.

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Radio
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TV
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All like radio, but with reachNetwork data. Introduction to Computer

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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.

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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 (by 2004)

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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)

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Communication medium over which people interact
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FTP, NFS, AFS (1980’s)

email (1980’s), on-line chat rooms, instant messaging (1990’s) audio, video (1990’s)
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A medium for information dissemination
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replacing telephone network?

USENET (1980’s) WWW (1990’s)
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audio, video (1990’s)
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replacing newspaper, magazine? 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, frien ds, 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

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World as a small village
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interactive sitcom

community organized according to interests  enhanced understanding among diverse groups

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What is Next?
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Electronic democracy
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Electronic terrorism
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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

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 long-haul and access communication links, customers own access links

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Wireless/Satellite companies
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Utility companies: power, water, railway
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alternative communication links

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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Internet Service Providers  Equipment companies
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own content

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Software companies

switches/routers, chips, optics, computers

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Commercial Internet after 1994
Joe's Company Campus Network Regional ISP Bartnet Xerox Parc SprintNet America On Line Stanford Berkeley

UUnet Network NSF IBM

NSF Network
Modem IBM Internet MCI

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Internet Physical Infrastructure
ISP Backbone ISP

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Residential Enterprise/ISP Access access, Backbone  Modem transmission  DSL
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Campus network
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Ethernet, ATM

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Cable modem Satellite

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T1/T3, DS-1 DS-3 OC-3, OC-12  access, regional, ATM vs. SONET, vs. backbone Introduction to Computer Network 32 WDM

Internet Service Providers

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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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