Prof. Younghee Lee 1 1 Computer Networks u Lecture 1: Introduction Prof. Younghee Lee u Some part of this teaching materials are prepared referencing the lecture note made by F. Kurose and Keith W. Ross

Prof. Younghee Lee 2 2 Computer Networks  Overview oIt introduces the concepts clearly first. oIt examines network applications oclient-server model, socket API, DNS, file transfer, Web browsing. oFinally, the explanation of how the underlying communication component works, fundamental of packet switching, basic principles of various Internet protocols including Protocols such as IP, TCP, ICMP, ARP etc. oThe course involves lecture, reading/discussion and homework. Room 635, , oOffice hour: 13:30-14:30 (M) &15:00-16:30 (W) Or by appointment  Text oComputer Networking: A Top-down Approach Featuring the Internet Third edition by Jim Kurose and Keith Ross, Addison Wesley, 2005  TA oTung, Tao: Room 617:

Prof. Younghee Lee 3 3 Computer Networks? u Computer Networks: Interconnected Collection of Autonomous Computers –Bus, LAN, MAN, WAN u (The Internet, The TCP/IP Internet): The set of subnetwork that are interconnected through TCP/IP –interconnection of many networks:an internetwork => an internet

Prof. Younghee Lee 4 4 The Internet?

Prof. Younghee Lee 5 5 What’s the Internet: “nuts and bolts” view u protocols: control sending, receiving of msgs –e.g., TCP, IP, HTTP, FTP, PPP u Internet: “network of networks” –loosely hierarchical –public Internet versus private intranet u Internet standards –RFC: Request for comments –IETF: Internet Engineering Task Force local ISP company network regional ISP router workstation server mobile

Prof. Younghee Lee 6 6 Computer Networks? 0.1 m Circuit board Data flow machine 1m System Multiprocessor 10m Room 100m Building Local Network 1km Campus 10km City Metropolitan Area 100km Country (Wide Area) Network 1,000km Continent 10,000km Planet The Internet

Prof. Younghee Lee 7 7 Computer Networks: Bandwidth- Distance Characteristics Data RateMPS (BPS) Local Area Network WAN MPS : Multi-Processor System Distance, meters

Prof. Younghee Lee 8 8 Applications of computer networks u Access to Remote Programs –Simulation, Computer Aided Ed.,, Medical Diagnosis u Access to Remote Data Bases –Reservations For Hotels, Airplanes, Home Banking –Automated Newspaper, Automated Library –Access to Information System: (e.g. World Wide Web) u Communication Medium –Electronic Funds Transfer System, Electronic Mail, Teleconferencing –Worldwide Newsgroups, International Contacts by Humans u Entertainment Industry –Video On Demand, Multiperson real-time simulation games –Selecting any movie/TV program ever made –Live TV may becomes interactive with audience u Pervasive computing –Context-aware networking –Resource Management for Application-Aware Networks –Autoconfiguration, Registration, Mobility management –Service discovery for wireless ad hoc network

Prof. Younghee Lee 9 9 Lecture Contents u Introduction, Protocols and layering u Applications: Client- server, Socket, DNS, , Web, SNMP, Security u TCP, UDP u Internetworking: Concepts, Architecture, and Protocols u Routing Principle, Internet Routing u IP, ARP, ICMP, Mobile networks u LAN, Hub, Wireless Link, PPP, WAN, ATM u Performance Modeling and Estimation u Multimedia Networking, Stream Protocols u Security in computer network u Network management

Prof. Younghee Lee 10 Evaluation u Evaluation –Assignment20% –Midterm exam30% –Final exam30% –Quiz15% –Class participation5%

Prof. Younghee Lee 11 A brief Computer Networks History u Centralized: Communication within a single system u Decentralized: Communications between geographically separated component of system u Distributed: Network communications between systems u Transparent: Networking without explicit network related commands(acces, Location, Control, Execution(process migration, load balancing)) –Definition of System: a self-contained entity capable of autonomous operation

Prof. Younghee Lee 12 Internet History u 1961: Kleinrock - queueing theory shows effectiveness of packet- switching u 1964: Baran - packet- switching in military nets u 1967: ARPAnet conceived by Advanced Research Projects Agency u 1969: first ARPAnet node operational u 1972: –ARPAnet demonstrated publicly –NCP (Network Control Protocol) first host- host protocol –first program –ARPAnet has 15 nodes : Early packet-switching principles

Prof. Younghee Lee 13 Internet History u 1970: ALOHAnet satellite network in Hawaii u 1973: Metcalfe’s PhD thesis proposes Ethernet u 1974: Cerf and Kahn - architecture for interconnecting networks u late70’s: proprietary architectures: DECnet, SNA, XNA u late 70’s: switching fixed length packets (ATM precursor) u 1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: –minimalism, autonomy - no internal changes required to interconnect networks –best effort service model –stateless routers –decentralized control define today’s Internet architecture : Internetworking, new and proprietary nets

Prof. Younghee Lee 14 Internet History u 1983: deployment of TCP/IP u 1982: smtp protocol defined u 1983: DNS defined for name-to-IP-address translation u 1985: ftp protocol defined u 1988: TCP congestion control u new national networks: Csnet, BITnet, NSFnet, Minitel u 100,000 hosts connected to confederation of networks u ITU Packet switch protocols: X.25… –Expected to be more popular : new protocols, a proliferation of networks

Prof. Younghee Lee 15 Internet History u Early 1990’s: ARPAnet decomissioned u 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) u early 1990s: WWW –hypertext [Bush 1945, Nelson 1960’s] –HTML, http: Berners-Lee –1994: Mosaic, later Netscape –late 1990’s: commercialization of the WWW Late 1990’s: u est. 50 million computers on Internet u est. 100 million+ users u backbone links runnning at 1 Gbps 1990 ’ s: commercialization, the WWW u ITU Packet switch protocols: X.25… –Expected to be more popular –TCP/IP win!: –Web protocols are available first on the top of TCP/IP –X. protocol products were introduced to market too late and expensive.

Prof. Younghee Lee 16 The need for Speed and Quality of service u The emergence of High Speed LANs (Amdahl's rule) u Multimedia applications –Video Conference –VoD –Live broadcasting u Mobility u Embedded Network u Network support for Pervasive computing –Service discovery, autoconfiguration