1. 1 Computer Networking Yang Xianchun Department of Computer Science Nanjing University

2. 2 Agenda  Course information r What is network? r A brief introduction to the Internet’s m past m present r Summary

3. 3 Course Information r Instructor  Yangxianchun ( 杨献春 ) Major in Computer Architecture and graduated from Nanjing University Interested in Distributed / Parallel Computing and Networking Senior Engineer of the State Key Laboratory for Novel Software at NJU E-mail: xcy@nju.edu.cn – E-mail is the best way to communicate with me Tel: 025-83593467

4. 4 Course Information (Syllabus) r What is this course about? m Introductory (first) course in computer networking learn principles of computer networking learn practice of computer networking Internet architecture/protocols as case study r Who is this course for? m Undergraduates, MS students r Prerequisites: m Algorithms: shortest path algorithms m programming skills: C/C++ or Java m Computer Organization m Operating Systems

5. 5 Course Information r Goals: m Have some fun, and learn about how modern networks work, with emphasis on the practical applications that most of you see and use every day Understand how Internet works –Its philosophy –Its protocols and mechanisms Learn network programming Have fun! –Are you happy with no Internet access in your life ? m Not a study of the OSI model, or older technologies and protocols. m Not a certification course for Network Specialists. m Not a study of network hardware or data communications equipment

6. 6 Course Information r Textbook m Computer Networking: A Top-Down Approach Featuring the Internet, 2nd, Kurose and Ross, 2002 r Reference books m Computer Networks, 4th edition, Andrew Tanenbaum, 2003 m Data and Computer communications, 7th edition, William Stallings, 2003 m 计算机网络, 第四版, 谢希仁, 2003 r Resource m Home page: http://cs.nju.edu.cn/yangxc m J.Kurose’s WWW site: gaia.cs.umass.edu/cmpsci_591_453

7. 7 Authors of the textbook r Dr. Jim Kurose m Professor and chair of the Department of Computer Science at the University of Massachusetts, Amherst m Eight-time recipient of the Outstanding Teacher Award from the National technology University r Dr. Keith Rose m Chair of the multimedia Communications Department at Institute Eurocom m From 1985 through 1997 he was a professor of the Department of System Engineering at the University of Pennsylvania

8. 8 Why using this book ? r New content – this is a fast- changing area r But more important, new structure and target Top-down Featuring the Internet 计算机网络：以 Internet 为特色的自顶向下方法 Computer Networking: A Top-Down Approach Featuring the Internet A Top-Down Approach Featuring the Internet Application Presentation Session Transport Network Data Link Physical

9. 9 A top-down approach: We’ll cover networking top-down r end-system applications, end-end transport r network core: routing, hooking nets together r link-level protocols, e.g., Ethernet r other stuff: security, management, multimedia

10. 10 Course Information r Workload: r Schedule: m Lectures: 44 classes m Test & Exam: 4 classes m Labs: 12 classes Coursework approx amount approx % written homeworks 8 10% programming ass’n 3 20% class test 2 10% final exam 60%

11. 11 Course Overview: Part 1: Introduction (4 classes, text: Chapter 1) m Overview of network components m Internet architecture and design philosophy r What is the Internet, What is a protocol? r Network edge, network core, network access r Physical media r Delay, loss in packet-switched networks r Protocol layers, service models r Internet backbones, NAPs and ISPs r A brief history of networking, Internet

12. 12 Course Overview: Part 2: Application Layer (6 classes, text: Ch. 2) m How you get work done in the network m HTTP, Email, DNS r Principles of application-layer protocols r The World Wide Web: HTTP r File transfer: FTP r Electronic mail in the Internet r The Internet's directory service: DNS r Socket programming PROGRAMMING ASSIGNMENT 1

13. 13 Course Overview: Part 3: Transport Layer (5 classes, text Ch. 3) m Why your data gets there m reliability; congestion control; transport protocols: TCP/UDP r Transport-layer services and principles r Multiplexing and demultiplexing applications r Connectionless transport: UDP r Principles of reliable of data transfer r TCP case study PROGRAMMING ASSIGNMENT 2 r Principles of congestion control r TCP congestion control CLASS TEST 1 (1 class)

14. 14 Course Overview: Part 4: Network Layer (6 classes, text: Ch. 4) m How your data finds its way m routing; network protocols: IP/IPv6 r Introduction and network service model r Routing principles PROGRAMMING ASSIGNMENT 3 r Hierarchical routing r IP: the Internet Protocol r Routing in the Internet r What’s inside a router? r Mobile networks

15. 15 Course Overview: Part 5: Link Layer, LANs (8 classes, text: Ch. 5) m What ties the network pieces together m multiple access & various MAC; LAN interconnection r Introduction, services r Error detection, correction r Multiple access protocols, LANs r LAN addresses, ARP r Ethernet r Hubs, bridges, switches r Wireless LANs: IEEE 802.11 r PPP: the Point-to-Point protocol r ATM networks

16. 16 Course Overview: Part 6: Multimedia Networking (5 classes, text: Ch. 6) m How to transmit efficiently Media streaming r Multimedia Networking Applications r Streaming Stored Audio and Video r Making the Best of the Best-Effort Service r Beyond Best Effort r Scheduling and Policing Mechanisms r Integrated Services r RSVP r Differentiated Services CLASS TEST 2 (1 class)

17. 17 Course Overview: Part 7: Network Security (6 classes, text: Ch. 7) m Who’s out there? Meet Bob, Alice & Trudy r What is network security? r Principles of cryptography r Authentication: Who are you? r Integrity r Key distribution, certification r Firewalls r Attacks, countermeasures r Case studies: secure e-mail, SSL, IPsec, 802.11 WEP

18. 18 Course Overview: Part 8: Network Management (4 classes, text: Ch. 8) m Help monitor, manage, and control your network r What is Network Management? r Internet Network Management Framework, SNMP r ASN.1 FINAL EXAM (2 classes)

19. 19 Agenda r Course information  What is network? r A brief introduction to the Internet’s m past m present r Summary

20. 20 What is Network? r Telephone network r Dialup r Public data network r Local area network r Internet r Mobile phone r … Nodes -- Interconnected

21. 21 Why Internet ? r The most successful network m Open m Heterogeneous m Simple network, complex end-terminals End-to-end argument r How about other networks? m Telephone m Mobile phone m Wireless LAN m Cable TV r IP convergence…

22. 22 Motivation: Communication r Need some common interface to communicate  network protocol r A->B: Hi r B->A: Hi r A->B: What time is it ? r B->A: 1:00pm r What if no protocol… r Woi kx ioa nio ? r #@!>? … r …

23. 23 An Example: Simple Mail Transfer Protocol (SMTP) r Scenario m Email client: Outlook, TheBat, NetscapeMail … m Email server: in Unix, Windows … r Messages from a client to a mail server m HELO m MAIL FROM: m RCPT TO: m DATA m QUIT r Messages from a mail server to a client m status code –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. m mail body user mailbox outgoing message queue mail server user agent user agent user agent mail server user agent user agent mail server user agent SMTP POP3, IMAP SMTP

24. 24 Internet Standardization Process r All standards of the Internet are published as RFC (Request for Comments) m but not all RFCs are Internet Standards ! but not all RFCs are Internet Standards ! m available: http://www.ietf.org m Till now: RFC3099 r A typical (but not the only) way of standardization: m Internet draft m RFC m Proposed standard m Draft standard (requires 2 working implementations) m Internet standard (declared by Internet Architecture Board)

25. 25 Agenda r Course information r What is a network?  A brief introduction to the Internet’s  past  present r Summary

26. 26 A Brief History of the Internet r 1957 m USSR launches Sputnik, US formed Advanced Research Projects Agency (ARPA) as a response r 1968 m Bolt Beranek and Newman, Inc. (BBN) was awarded Packet Switch contract to build Interface Message Processors (IMPs) for ARPANET

27. 27 r 1969 m ARPANET commissioned: 4 nodes, 50kbps A Brief History of the Internet

28. 28 Initial Expansion of the ARPANET Dec. 1969March 1971July 1970 Apr. 1972 Sep. 1972

29. 29 Multiple Networks r 1974: Initial design of TCP to connect multiple networks r 1986: NSF builds NSFNET as backbone, links 6 supercomputer centers, 56 kbps; this allows an explosion of connections, especially from universities r 1987: 10,000 hosts r 1989: 100,000 hosts WELCOME by Leonard Kleinrock …

30. 30 Web and Commercialization of the Internet r 1991: NSF lifts restrictions on the commercial use of the Net; World Wide Web released r 1992: 1 million hosts r 2002: backbones run at 10Gbps, 100s millions computers in 150 countries r Internet history and Timeline m http://www.zakon.org/robert/internet/timeline/ http://www.zakon.org/robert/internet/timeline/

31. 31 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

32. 32 Backbone: National ISP Local/Regional ISP Local/Regional ISP Internet Physical Infrastructure r Residential Access m Modem m DSL m Cable modem r Access to ISP, Backbone transmission m T1/T3, OC-3, OC-12 m ATM, SONET, WDM r Internet Service Providers m Local/Regional/Natio nal m They exchange packets at Point of Presence (POP) r Campus network access m Ethernet m FDDI m Wireless

33. 33 Local Access: ADSL r Asymmetrical Digital Subscriber Line (ADSL) r Telephone company’s solution to “last mile problem”

34. 34 Local Access: Cable Modems r Fiber node: 500 - 1K homes r Distribution hub: 20K - 40 K homes r Regional headend: 200 K - 400 K homes

35. 35 From AT&T web site. AT&T US Internet Backbone

36. 36 Canadian 2G National Internet Backbone From http://www.canarie.ca/canet4/connected/canet4_map.html

37. 37 AT&T Global Backbone IP Network From http://www.business.att.com

38. 38 Web and Commercialization of the Internet http://research.lumeta.com/ches/map/

39. 39 Internet applications - FTP

40. 40 Internet applications - Email

41. 41 Internet applications – WWW 1990 -

42. 42 Internet applications – P2P 2000-

43. 43 Internet applications- what’s next ? r Media streaming (Internet TV) r E-commerce r Online game r …

44. 44 Summary r Course information r Network: nodes -> interconnected r Protocol: format and the order of messages exchanged, as well as the actions taken r Internet: The past: m started as ARPANET: late 1960s m initial link bandwidth: 50 kbps m number of hosts: 4 r Internet: Current: m number of hosts: grows at an exponential speed July 2002 was about 162 millions m backbone speed: 10 Gbps

45. 45 Practices r Log into a Unix machine (or Windows) r Read the manual of ping and traceroute, and try them on a machine m % /bin/ping m % /usr/sbin/traceroute  Look at the web sites of the routers you see through traceroute

46. 46 Slides’ Source r Jim Kurose m kurose@cs.umass.edu m http:// gaia.cs.umass.edu/cmpsci_591_453 r Jiangchuan Liu m jcliu@cs.sfu.ca m http:// www.cs.sfu.ca/~jcliu/cmpt371 r Gergely Zaruba m zaruba@uta.edu m http://crystal.uta.edu/~zaruba