Computer Networks

1. Computer Networks Ilam University Dr. Mozafar Bag-Mohammadi Introduction to Computer Network

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

3. Course Materials • Course Web page • visit regularly • Textbook • “Computer Networks, A system approach”. Peterson & Davie 4th edition • مهندسی اینترنت، احسان ملکیان، انتشارات نص • Grading • Midterm 35% • Final 55% • homework 10% • پر کردن فرم عدم تقلب در تمرینات Introduction to Computer Network

4. Prerequisition • General knowledge in Computer. • Fluency in English, specially reading. • C++ programming. • Knowledge of UNIX (LINUX) system and programming. Introduction to Computer Network

5. Communication as 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. Introduction to Computer Network

6. Primary Communication means • Language • Conventions • Body Language, • Meta language. • Universal. • Problems: • Limited in Time and space. • We are struggling all the history to overcome these limitation. Introduction to Computer Network

7. Communication elements • Producer, Sender • Speaker • Consumer, Receiver • Listener • They both do processing and have limitation • Message - Talk • Transfer media, like air • Substance • Capacity • Delay Introduction to Computer Network

8. Type of communication • One to one • Direct talk. • One to many • Talks, conferencing • Many to Many • Like mass media, newspaper. • Domain of communication • Small, primary society • Medium, more developed society. • Large, more advance society. Introduction to Computer Network

9. 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 Introduction to Computer Network

10. 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. Introduction to Computer Network

11. 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. Introduction to Computer Network

12. 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 Introduction to Computer Network

13. Broadcast media • Printing, newspapers, • 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 richer data. Introduction to Computer Network

14. 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. Introduction to Computer Network

15. 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 2.4 Gbps, 200 millions computers in 150 countries Introduction to Computer Network

16. 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/ Introduction to Computer Network

17. Recent Growth (1991-2000) Introduction to Computer Network

18. 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 • email (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? Introduction to Computer Network

19. 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 Introduction to Computer Network

20. Today’s Vision • Electronic commerce • virtual enterprise • Internet entertainment • interactive sitcom • World as a small village • community organized according to interests • enhanced understanding among diverse groups • 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 Introduction to Computer Network

21. 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 • Medium companies • own content • Internet Service Providers • Equipment companies • switches/routers, chips, optics, computers • Software companies Introduction to Computer Network

22. What is Next? • Who knows?!! • Use your imagination • If you can predict something here you will be a winner • Peer to peer • Ebay • Google • weblogs Introduction to Computer Network

23. 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 Introduction to Computer Network

24. Internet Physical Infrastructure Backbone ISP • Residential Access • Modem • DSL • Cable modem • Satellite ISP • 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) Introduction to Computer Network