COSC6377: Computer Networks

1. Introduction 1-1 COSC6377: Computer Networks Rong Zheng rzheng@cs.uh.edu

2. Introduction 1-2 Introduction Overview of the course Basic concepts and structures in computer networking Network architecture

3. Introduction 1-3 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?

4. Introduction 1-4 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) Chap 1.3Chap 1.3

5. Introduction 1-5 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/webcast.html David Clark et al �end2end arguments� Van Jacobson, TCP congestion control Robert Metcalfe, inventor of Ethernet �

6. Introduction 1-6 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

7. Introduction 1-7 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

8. Introduction 1-8 Growth of the Internet Internet bandwidth Nielsen�s law: 50% each year What do you gather from the data?What do you gather from the data?

9. Introduction 1-9

10. Introduction 1-10 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. Introduction 1-11 A Few Words on Networking Research Wireless System Research Group (WiSeR) http://coco.cs.uh.edu/~rzheng

12. Introduction 1-12 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. Introduction 1-13 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. Introduction 1-14 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. Introduction 1-15 Introduction Overview of the course Basic concepts and structures in computer networking Network architecture

16. Introduction 1-16 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

17. Introduction 1-17 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

18. Introduction 1-18 Network Components (Examples)

19. Introduction 1-19 Juniper Routers

20. Introduction 1-20 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

21. Introduction 1-21 Tier-1 ISP: e.g., Sprint

22. Introduction 1-22 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

23. Introduction 1-23 Internet structure: network of networks �Tier-3� ISPs and local ISPs last hop (�access�) network (closest to end systems)

24. Introduction 1-24 Internet structure: network of networks a packet passes through many networks!