Univ. ov TehranIntroduction to Computer Network1 Computer Networks An Introduction to Computer Networks University of Tehran Dept. of EE and Computer Engineering By: Dr. Nasser Yazdani Lecture 1: Introduction

Univ. ov TehranIntroduction to Computer Network2 Outline Agenda Policy, Grading, reading materials, etc. Communication. Overview and history of the Internet

Univ. ov TehranIntroduction to Computer Network3 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.

Univ. ov TehranIntroduction to Computer Network4 Course Materials Course Web page visit regularly Textbook “Computer Networks, A system approach”. Peterson & Davie 3 rd edition

Univ. ov TehranIntroduction to Computer Network5 Grading Homework assignments, around % five homework and a small project. Severe late penalties! Midterm exam around %35. Final exam around %35.

Univ. ov TehranIntroduction to Computer Network6 Prerequisition General knowledge in Computer engineering. C programming. Knowledge of UNIX (LINUX) system and programming. Fluency in English, specially reading.

Univ. ov TehranIntroduction to Computer Network7 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.

Univ. ov TehranIntroduction to Computer Network8 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.

Univ. ov TehranIntroduction to Computer Network9 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)

Univ. ov TehranIntroduction to Computer Network10 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.

Univ. ov TehranIntroduction to Computer Network11 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

Univ. ov TehranIntroduction to Computer Network12 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.

Univ. ov TehranIntroduction to Computer Network13 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.

Univ. ov TehranIntroduction to Computer Network14 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

Univ. ov TehranIntroduction to Computer Network15 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.

Univ. ov TehranIntroduction to Computer Network16 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.

Univ. ov TehranIntroduction to Computer Network17 History of the Internet 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

Univ. ov TehranIntroduction to Computer Network18 Growth of the Internet Number of Hosts on the Internet: Aug Oct ,024 Dec ,174 Oct ,000 Oct ,056,000 Apr ,706,000 Jul ,540,000 Jul ,249,900 Jul ,288,000 Data available at:

Univ. ov TehranIntroduction to Computer Network19 Recent Growth ( )

Univ. ov TehranIntroduction to Computer Network20 Services Provided by the Internet Shared access to computing resources telnet (1970’s) Shared access to data/files FTP, NFS, AFS (1980’s) Communication medium over which people interact (1980’s), on-line chat rooms, instant messaging (1990’s) audio, video (1990’s) replacing telephone network? A medium for information dissemination USENET (1980’s) WWW (1990’s) replacing newspaper, magazine? audio, video (1990’s) replacing radio, CD, TV?

Univ. ov TehranIntroduction to Computer Network21 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

Univ. ov TehranIntroduction to Computer Network22 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

Univ. ov TehranIntroduction to Computer Network23 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-not’s Electronic terrorism hacker can bring the whole world to its knee

Univ. ov TehranIntroduction to Computer Network24 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

Univ. ov TehranIntroduction to Computer Network25 Industrial Players Medium companies own content Internet Service Providers Equipment companies switches/routers, chips, optics, computers Software companies

Univ. ov TehranIntroduction to Computer Network26 Commercial Internet after 1994 NSF Network Regional ISP America On Line IBM Bartnet Campus Network Joe's Company Stanford Xerox Parc Berkeley NSF Network Internet MCI UUnet SprintNet Modem IBM

Univ. ov TehranIntroduction to Computer Network27 Backbone ISP Internet Physical Infrastructure 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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