Computer Network : Spring 2001

Transcription

1 Computer Network : Spring 2001 Prerequisite Data Communications Class Hour Monday 13:00-14:15 (lecture), by Yanghee Choi, Rm Wednesday 13:00-14:15 (practice), by, Course Web Page course Handout Web Page Practice / HW Web Page Textbook Comer vol.1 4/e Grading Practice, Homework, Exams, Attendance Contact yhchoi@snu.ac.kr

2 Course Schedule 1.(3/04) Overview 2.(3/11) Internet address & ARP 3.(3/18) IP, IPv6 4.(3/25) IP routing, ICMP 5.(4/01) Subnetting, UDP 6.(4/08) TCP 7.(4/15) TCP Congestion Control 8.(4/22) IGP 9.(4/29) Midterm Exam. 10.(5/06) Internet 2 11.(5/13) EGP 12.(5/20) Multicast 13.(5/27) Mobile IP, IP over ATM 14.(6/03) BOOTP, DHCP, DNS 15.(6/10) Internet Application, RTP 16.(6/17) Final Exam.

3 Practice Schedule Day Lecture Homework 3/6 CGI Simple CGI 3/13 Introduction to Java Java Applet 3/20 Internet Tool Practice Traffic measurement 3/27 Socket Programming (1) UDP echo server 4/3 Socket Programming (2) Proxy server 4/10 Routing (1) Routing table lookup alg. 4/17 Internet New Technology Paper 4/24 Routing (2) Distance vector routing alg 5/8 MPEG4 Paper 5/15 No class (Festival) 5/22 Multicast Chatting Server & Client 5/29 NS-2 Tool Ns install & topology 6/5 No lecture Ns FTP/CBR simulation

4 1. Introduction and Overview 4

5 Internet Timeline 3000 BC : Abacus 1642 : Pascal : numerical wheel calculator 1822 : Babbage : difference engine 1945 : Eckert : ENIAC 1969 : first ARPANET connection UCLA, SRI, UCSB, Utah 1972 : CYCLADES (France) 1974 : V. Cerf : TCP

6 Internet Timeline 1977 : over Telenet 1980 : IBM : Bitnet 1981 : IBM : PC 1982 : Time : Computer 1984 : Domain Name System 1988 : Morris : Worm, and CERT 1989 : number of hosts exceeds 100, : Al Gore : High Performance Computing Act 1991 : Berners-Lee : WWW 1992 : Internet Society 1993 : Andreessen : Mosaic 1994 : Yahoo!

7 History of Internet Started from ARPANET (ARPANET and MILNET) Implemented in BSD UNIX A set of utilities for network services Socket interface NSFNET backbone: interconnect supercomputer centers using TCP/IP protocols Rapid expansion -> problem of scale Insufficient address space, etc. IETF(Internet Engineering Task Force) defines technical standards 7

8 Internet Business (2001) 55 ( 41% ) 8 6 (23% ) Internet Portal E-business solutions Security Game Wireless Internet High Speed Internet

9 Future Post PC, auto PC Wireless Multimedia Home Networking All IP

10 Issues Business Models Contents, copyright Language Security Digital Divide

11 Motivation for Internetworking It is impossible to build a universal network from a single hardware technology Internetworking: Accommodates multiple, diverse underlying h/w technologies by providing a way to interconnect heterogeneous networks and a set of communication conventions 11

12 Why Network-Level? Application-Level Interconnection No flexibility, duplication of code, not robust Network-Level Interconnection - Internetworking Maps directly onto the underlying network hardware Separates data communication activities from application programs Builds general purpose communication facilities Possible to add new network technologies by modifying or adding a single piece of new network level software 12

13 Cont d Properties of the Internet Hide the underlying internet architecture from the user Do not mandate a network interconnection topology Share a universal set of machine identifiers(names, addresses) Network independence in the user interface 13

14 Internet Configuration subnet subnet Packet Host subnet Host Packet subnet Router subnet

15 Protocols Protocol: rules for communication Message formats, timing Describes how a computer responds when a message arrives Specifies how a computer handles errors or other abnormal conditions All network services are described by protocols 15

16 TCP/IP TCP/IP Internet Protocol Suite: resulted from research funded by the ARPA(Advanced Research Projects Agency) Features of TCP/IP services Network technology independence Universal Interconnection End-to-end acknowledgments Application protocol standards 16

17 Internet Services Application level Electronic mail File transfer Remote login WWW AV Game etc. Network level Connectionless packet delivery service Reliable stream transport service 17

18 develops interoperable technologies (specifications, guidelines, software, and tools) to lead the Web to its full potential led by Tim Berners-Lee, inventor of WWW MIT Laboratory for Computer Science (LCS) INRIA (France), Keio (Japan)

19 INTERNET USERS : WORLD

20 USERS : KOREA

21 Host Count : Korea

22 :

23 Internet : USA by CAIDA

24 Traffic : SNU - Koren

25 Internet Documents Internet-Drafts Working documents (works in progress) No status of any kind, not archived, deleted after 6 months Announced and disseminated by IETF Secretariat RFCs Archival document series of the IETF Not all RFCs are standards-track Edited, announced, and disseminated by RFC Editor

26 RFC(Requests For Comments) Internet RFC(Requests For Comments) Documentation of work on the Internet, proposals for new or revised protocols, and TCP/IP protocol standards Internet drafts: preliminary version of RFC 26

27 RFC Categories Standards Track Proposed Standard Draft Standard Standard Best Current Practices Informational Experimental Historic

28 The Internet Engineering Task Force (IETF)... is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual*. * From IETF Web page:

29 IETF Areas IETF Chair Harald Alvestrand Applications (app) Patrik Faltstrom Ned Freed Internet (int) Thomas Narten Erik Nordmark

30 IETF Areas(Cont.) Operations & Management (ops) Randy Bush Bert Wijnen Routing (rtg) Bill Fenner Randy Bush Security (sec) Jeffrey Schiller Marcus Leech

31 IETF Areas(Cont.) Sub-IP Scott Bradner Bert Wiinen Transport Services (tsv) Scott Bradner Allison Mankin User Services (usv) April Marine

32 Organization of the IETF Internet Engineering Steering Group (Area Directors, plus the IETF Chair) Area Director [Directorate] WG1, WG2, Area Director [Directorate] WG1, WG2, Area Director [Directorate] WG1, WG2,

33 Working Groups Rough consensus and running code... No formal voting Disputes resolved by discussion and demonstration Mailing list and face-to-face meetings Avoid Running Consensus and Rough Code Prototypes before standardization

34 Useful URLS IETF Home Page The Tao of the IETF Novice s Guide IESG Status Page Requests Page Working Group IETF Monthly Status Reports Additional Information

35 Subnetwork Technologies Two approaches to network communication Circuit-switched(connection-oriented) network pros) guaranteed capacity, cons) cost inefficient Packet-switched(connectionless) network pros) capacity sharing, cons) no guarantee for capacity WAN vs. LAN Wide Area Network: long distance, low speed, large delay Local Area Network: short distance, high speed, small delay 35

36 Network Examples PAN (Personal Area Network) DAN (Desk Area Network) Home Network Bluetooth, Cordless, HomeRF, PNA, Settop, Cable LAN Ethernet, ATM WAN ATM, MPLS, IP, Satellite, Optical Galactic

37 Ethernet Popular packet-switched LAN technology invented at Xerox in the early 1970s Xerox Co., Intel, and DEC standardized Ethernet in 1978 IEEE Variants 10 Mbps 100 Mbps (Fast Ethernet) Gbps (1, 10, 100) 37

38 Ethernet Basics Originally broadcast bus technology with best-effort delivery semantics and distributed access control - now star topology is used CSMA/CD(Carrier Sense Multiple Access / Collision Detection): exponential backoff algorithm - no longer necessary in switched Ethernet 48-bit Ethernet hardware address: unicast, broadcast, multicast address 38

39 Ethernet Ethernet frame format Preamble Destination Address Source Address Frame Type Frame Data CRC 8 octets 6 octets 6 octets 2 octets octets 4 octets Extending an Ethernet Repeater Bridge: packet filtering 39

40 ATM (Asynchronous Transfer Mode) High-speed connection-oriented networking technology for LAN and WAN ATM cell small fixed size packet 53 bytes = header(5) + data(48) VC(Virtual Channel), VP(Virtual Path), VCI(VC Identifier), VPI(VP Identifier) 40

41 ATM Concept A A A A B B A B B A A stream of cells B B