1. Introduction1-1 COSC6377: Computer Networks Rong Zheng rzheng@cs.uh.edu Computer Networking: A Top Down Approach Featuring the Internet, 3 rd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2004.

2. Introduction1-2 Introduction  Overview of the course  Basic concepts and structures in computer networking  Network architecture

3. Introduction1-3 Computer Networks  A computer network is a system for communication among two or more computers  What amounts to “computers”?  What kind of communication? – “digital”  System: both software & hardware  Examples? Our focus is on the Internet

4. Introduction1-4 History of the Internet  61-72: development of packet switching  72-80: Proprietary networks and internetworking  Multiple packet switching networks  “Networks of networks”: earlier development of TCP, UDP, IP  ALOHA, Ethernet  80-90: proliferation of networks  Standardization of networking protocols TCP/IP, DNS etc  NSF builds NSFNET as backbone, links 6 Supercomputer centers, 1.5 Mbps, 10,000 computers  90’s: Internet explosion  94: NSF backbone dismantled, multiple private backbones  Emergence of World Wide Web (invented by Time Berners-Lee)

5. Introduction1-5 Internet “Hall of Fame”  Al Gore, former vice president of USA  Vinton G. Cerf and Robert E. Kahn  2004 Turing Award winner “For pioneering work on internetworking, including the design and implementation of the Internet's basic communications protocols, TCP/IP, and for inspired leadership in networking”  Turing lecture: http://www.acm.org/sigs/sigcomm/sigcomm2005/webcas t.html http://www.acm.org/sigs/sigcomm/sigcomm2005/webcas t.html  David Clark et al “end2end arguments”  Van Jacobson, TCP congestion control  Robert Metcalfe, inventor of Ethernet ……

6. Introduction1-6 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 Jan. 1997 16,146,000 Jan. 1999 56,218,000 Jan. 2001 109,374,000 Jan 2003 171,638,297 Data available at: http://www.isc.org/

7. Introduction1-7 Growth of the Internet  Traffic on Internet (in TB/mo) 1990 1.0 1991 2.0 1992 4.4 1993 8.3 1994 16.3 1996 1,500 1997 2,500 - 4,000 1998 5,000 - 8,000 1999 10,000 - 16,000 2000 20,000 - 35,000 2001 40,000 - 70,000 2002 80,000 - 140,000 Andrew Odlyzko, “Internet traffic growth: Sources and implications”

8. Introduction1-8 Growth of the Internet  Internet bandwidth  Nielsen’s law: 50% each year Projected

9. Introduction1-9

10. Introduction1-10 What is Next Big Thing?  I wish I have the answer  Technology  Wireless broadband networks  Optical switching networks (?)  Application  VOIP  Peer-to-peer applications  Online gaming Sony’s EverQuest servers host 600,000 PC gamers

11. Introduction1-11 A Few Words on Networking Research  Wireless System Research Group (WiSeR) http://coco.cs.uh.edu/~rzheng Information Theory Distributed Systems Grid Computing Computer Networking Combinatorics/ Graph theory Probability/ Stochastic techniques 1.Protocol design 2.Performance modeling, analysis 3.System building Data structure, algorithms, complexity theory Application Domains Wireless Management Security

12. Introduction1-12 What will be covered?  Network architecture, services, apps  TCP/IP  Protocol details  Algorithms  Performance analysis  Ethernet, Wireless networks  Multimedia networks  QoS scheduling  Signaling  Network security  Basic knowledge  Attacks and counter-measures  Network management

13. Introduction1-13 What will not be covered?  Socket programming (chap 2.7-2.9)  Physical layer technologies (chap 1.4)  Cellular networks  Multicast routing (chap 4.7)  ATM, frame relay, PPP (chap 5.7-5.8) The emphasis is no only on “how” but also “why”  Knowledge base  Reasoning behind the design

14. Introduction1-14 Logistics  Textbook, reference book  Office hour  Homework, project policy  Grade  Prerequisite test:  What are the OSI-ISO layers? How is it related to the practice in the Internet?  What is protocol?  What is the difference between packet switching and circuit switching?  Sockets

15. Introduction1-15 Introduction  Overview of the course  Basic concepts and structures in computer networking  Network architecture

16. Introduction1-16 What’s the Internet: “nuts and bolts” view  End systems  Host computer  Network applications  Access networks  Local area networks  communication links  Network core:  routers  network of networks local ISP company network regional ISP router workstation server mobile

17. Introduction1-17 What’s the Internet: “nuts and bolts” view  Protocols control sending, receiving of msgs  e.g., TCP, IP, HTTP, FTP, PPP  Internet: “network of networks”  loosely hierarchical  public Internet versus private intranet  Internet standards  RFC: Request for comments  IETF: Internet Engineering Task Force local ISP company network regional ISP router workstation server mobile

18. Introduction1-18 Network Components (Examples) Fibers Coaxial Cable LinksInterfacesSwitches/routers Ethernet card Wireless card Large router Switch

19. Introduction1-19 Juniper Routers

20. Introduction1-20 Internet structure: network of networks  roughly hierarchical  at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T, Cable and Wireless), national/international coverage  treat each other as equals Tier 1 ISP Tier-1 providers interconnect (peer) privately NAP Tier-1 providers also interconnect at public network access points (NAPs)

21. Introduction1-21 Tier-1 ISP: e.g., Sprint Sprint US backbone network Seattle Atlanta Chicago Roachdale Stockton San Jose Anaheim Fort Worth Orlando Kansas City Cheyenne New York Pennsauken Relay Wash. DC Tacoma DS3 (45 Mbps) OC3 (155 Mbps) OC12 (622 Mbps) OC48 (2.4 Gbps)

22. Introduction1-22 Internet structure: network of networks  “Tier-2” ISPs: smaller (often regional) ISPs  Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier 1 ISP NAP Tier-2 ISP Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet  tier-2 ISP is customer of tier-1 provider Tier-2 ISPs also peer privately with each other, interconnect at NAP

23. Introduction1-23 Internet structure: network of networks  “Tier-3” ISPs and local ISPs  last hop (“access”) network (closest to end systems) Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet

24. Introduction1-24 Internet structure: network of networks  a packet passes through many networks! Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP