CSE 245: Computer Networks and Data Communication cse.uconn/~jcui/courses/cse245/

1. CSE 245: Computer Networks and Data Communicationhttp://www.cse.uconn.edu/~jcui/courses/cse245/ Jun-Hong Cui 08/26/2003

2. Outline • Course information • What is a network protocol? • A brief introduction to the Internet: past and present • Summary

3. Course Information • Personnel • instructor • Jun-Hong Cui, jcui@cse.uconn.edu, ITEB 267 • office hours • TuTh 03:30pm-4:30pm or by appointments • Feel free to stop by if you see my door open: ITEB 267 • e-mail is the best way to communicate with me • grader • TBA

4. Course Information • Textbook • Computer Networking: A Top-Down Approach Featuring the Internet, 2/e by Kurose and Ross • Reference books • Computer Networks, 4/e by Andrew Tanenbaum • Unix Network Programming by W. Richard Stevens And more (see handout) • Resource • Home page • http://www.cse.uconn.edu/~jcui/courses/cse245/ • Mailing list • TBA

5. What Are the Goals Of This Course? • Understand how Internet works • Its philosophy • Its protocols and mechanisms • Learn network programming • Have fun!

6. What Will We Cover? • Introduction (3 lectures) • Internet architecture and design philosophy • Applications (4 lectures) • HTTP, Email, DNS • transport services (4 lectures) • reliability; congestion control; transport protocols: TCP/UDP • network services (5 lectures) • routing; network protocols: IP/IPv6 • link and physical layers (4 lectures) • multiple access; Ethernet, FDDI, hubs and bridges • multimedia networking & security (if time permits) • audio/video applications; network support

7. What Do You Need To Do? • Your prerequisites • algorithms: e.g. shortest path algorithms • programming: C/C++, or Java • basic concepts of operating systems • Your workload • reading assignment for every lecture • homework assignments • 4 written assignments • 2 programming projects • one mid-term exam, and one final exam

8. More important is what you learn than the grades Grading

9. Class Survey • Please take the class survey • help me to determine your background • help me to determine the depth and topics • any suggestions on the tentative schedule http://www.cse.uconn.edu/~jcui/courses/cse245/schedule.html

10. Questions?

11. Outline • Course information • What is a network protocol? • A brief introduction to the Internet: past and present • Summary

12. What is a Network Protocol? • A network protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

13. user agent user agent user agent user agent user agent user agent SMTP SMTP SMTP POP3, IMAPSMTP mail server mail server mail server outgoing message queue user mailbox An Example: Simple Mail Transfer Protocol (SMTP) • Messages from a client to a mail server • HELO • MAIL FROM: <address> • RCPT TO: <address> • DATA<This is the text end with a line with a single .> • QUIT • Messages from a mail server to a client • status code • The first digit of the response broadly indicates the success, failure, or progress of the previous command. • 1xx - Informative message • 2xx - Command ok • 3xx - Command ok so far, send the rest of it. • 4xx - Command was correct, but couldn't be performed for some reason. • 5xx - Command unimplemented, or incorrect, or a serious program error occurred. • content

14. Internet Standardization Process • All standards of the Internet are published as RFC (Request for Comments) • but not all RFCs are Internet Standards ! • available: http://www.ietf.org • A typical (but not the only) way of standardization: • Internet draft • RFC • Proposed standard • Draft standard (requires 2 working implementations) • Internet standard (declared by Internet Architecture Board)

15. Outline • Course information • What is a network protocol? • A brief introduction to the Internet • past • present • Summary

16. A Brief History of the Internet • 1957 • USSR launches Sputnik, US formed Advanced Research Projects Agency (ARPA) as a response • 1968 • Bolt Beranek and Newman, Inc. (BBN) was awarded Packet Switch contract to build Interface Message Processors (IMPs) for ARPANET

17. A Brief History of the Internet • 1969 • ARPANET commissioned: 4 nodes, 50kbps

18. Initial Expansion of the ARPANET Dec. 1969 July 1970 March 1971 Apr. 1972 Sep. 1972

19. Multiple Networks • 1974: Initial design of TCP to connect multiple networks • 1986: NSF builds NSFNET as backbone, links 6 supercomputer centers, 56 kbps; this allows an explosion of connections, especially from universities • 1987: 10,000 hosts • 1988: NSFNET backbone upgrades to 1.5Mbps • 1989: 100,000 hostsWELCOME by Leonard Kleinrock …

20. Web and Commercialization of the Internet • 1990: ARPANET ceases to exist • 1991: NSF lifts restrictions on the commercial use of the Net; Berners-Lee of European Organization for Nuclear Research (CERN) released World Wide Web • 1992: 1 million hosts • 1994: NSF reverts back to research network (vBNS); the backbone of the Internet consists of multiple private backbones • Today: backbones run at 10Gbps, 100s millions computers in 150 countries

21. Growth of the Internet in Terms of Number of Hosts Number of Hosts on the Internet: Aug. 1981 213 Oct. 1984 1,024 Dec. 1987 28,174 Oct. 1990 313,000 Jul. 1993 1,776,000 Jul. 1996 19,540,000 Jul. 2000 93,047,000 Jul. 2002 162,128,493

22. Outline • Course information • What is a network protocol? • A brief introduction to the Internet • past • present • Summary

23. Internet Physical Infrastructure Local/Regional ISP Backbone:National ISP Local/RegionalISP • Residential Access • Modem • DSL • Cable modem • Internet Service Providers • Local/Regional/National • They exchange packets at Point of Presence (POP) • Access to ISP, Backbone transmission • T1/T3, OC-3, OC-12 • ATM, SONET, WDM • Campus network access • Ethernet • FDDI • Wireless

24. Local Access: ADSL • Asymmetrical Digital Subscriber Line (ADSL) • Telephone company’s solution to “last mile problem”

25. Local Access: Cable Modems • Fiber node: 500 - 1K homes • Distribution hub: 20K - 40 K homes • Regional headend: 200 K - 400 K homes

26. ATT Global Backbone IP Network From http://www.business.att.com

27. From AT&T web site.

28. Network Access Point • Interconnect multiple ISP’s

29. Summary • Course information • A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. • The past: • The Internet started as ARPANET in late 1960s • The initial link bandwidth was 50 kbps • The number of hosts at the end of 1969 was 4 • Current: • The number of hosts connected to the Internet grows at an exponential speed • The backbone speed of the current Internet is about 10 Gbps • The number of hosts attached to the Internet in July 2002 was about 162 millions

30. local ISP local ISP NAP NAP Summary: Internet structure: network of networks • roughly hierarchical • national/international backbone providers (NBPs) • e.g. BBN/GTE, Sprint, AT&T, IBM, UUNet • interconnect (peer) with each other privately, or at public Network Access Point (NAPs) • regional ISPs • connect into NBPs • local ISPs • connect into regional ISPs regional ISP NBP B NBP A regional ISP

31. Hands-on Exercises • Read the manual of ping and traceroute, and try them on an ECS machine • % /bin/ping <machine_name> • % /usr/sbin/traceroute <machine_name> • Look at the web sites of the routers you see through traceroute • Have fun …