1. 1 CS716 Advanced Computer Networks By A. Wahid Shaikh

2. Lecture No. 1

3. 3 Instructor’s Introduction Ph.D. Mobile Wireless Net., Univ. of Paris-Sud, France –Elect. Engg.,U.E.T. Lahore –M.S. Comp. Engg., E.S.I.M., France –D.E.A. Parallel Comp. Arch., Univ. of Paris-Sud, France Active participant of MANET wg of IETF since 1997 –Co-author of an RFC on routing protocol for MANETs Associated with INRIA, France as a research fellow –Worked on Praxitele, PRIMA and IPANEMA projects Protocol implement. experience at Enabling Technologies –Implementation of RTP-RTCP/UDP-TCP/IP stack for a RISC based packet processor, including CRTP, PPP/MP, IPsec, QoS. Currently working at CARE Pvt. Ltd. and CASE –Design/development of long-range, secure mobile ad hoc networks

4. 4 Significance and Rationale of course Networks and telecommunication is getting more and more importance Future telecomm networks will be more oriented toward “networks” rather than “communication” Widespread Internet, diffused in our daily life is a ground reality; its beneficial to understand it Its fun to play with protocols (software) and able to design exciting new type of networks

5. 5 Foundation Course in Network Stream This Computer Networks course is a foundation course for “Networks” as the Area of Specialization It is a required pre-requisite course for the following advanced level courses in networking –Performance Analysis of Communication Networks –Integrated Services over Packet Networks –Computer Network Security –Mobile Networking It is a recommended pre-requisite for the course: –Network and System Programming

6. 6 Course Material Reference books –Many textbooks on Networking may be consulted Lot of research papers! –Many will be made available on course web site RFCs and Internet drafts –Related to TCP/IP suite and other protocols Web resources –Tutorials, white papers, reports, etc.

7. 7 Text Book Larry L. Peterson and Bruce S. Davies, Computer Networks: A Systems Approach –Third Edition [2003], Morgan Kaufmann Publishers, San Mateo, California, USA W. Richard Stevens, UNIX Network Programming, Volume 1, (Networking APIs: Sockets and XTI) –Second Edition, Prentice Hall –Recommended ONLY for programming part

8. 8 Prerequisites Required: An undergraduate level course on computer networks Good knowledge of C language, preferably in Unix/Linux –e.g. C and Data Structures course

9. 9 Course Evaluation Assignments Quizzes Research Papers Term Projects / Reports Midterm exam Final exam

10. 10 Expectations What do you want (or expect) to learn from this course ?

11. 11 Expectations This course IS about … –Network principles and concepts –General purpose computer networks –Internet perspective Major components of the Internet protocol suite –Network software –Designing and building a system

12. 12 Expectations This course IS NOT about … –Survey of existing protocol standards –Specialized networks (e.g. CATV, telephone) –OSI perspective –Network hardware Data transmission on physical layer –Queuing theory (we do survey, if time permits)

13. 13 Expectations We will learn why networks are like they are

14. 14 Objectives: Principles and Concepts At the end of this course, you should be able to: –Identify the problems that arise in networked communication –Explain advantages/disadvantages of existing solutions to these problems in different networking scenarios –Evaluate novel approaches to these problems –Understand the components of Internet protocol suite –Understand the implications of a given solution for performance in various networking environments

15. 15 Objectives: Programming At the end of this course, you should be able to: –Identify and describe the purpose of each component of the TCP/IP protocol suite –Develop client-server applications using TCP/IP –Understand the impact of trends in network hardware on network software issues –Understand over 1000 useful (or useless) VUAs

16. 16 Course Contents Overview Introduction to network programming Direct link networks Packet switching Internetworking End-to-end protocols Congestion control and resource allocation End-to-end data Applications Performance analysis and queuing theory (?)

17. 17 Introduction Outline –Statistical Multiplexing –Inter-Process Communication –Performance Metrics –Network Architecture

18. 18 What is Your Over-ambitious Goal ? Build a computer network which –Can grow to global proportions –Support diverse applications Then … think about –Underlying building blocks Which available technologies to use –Integrating the blocks to communicate Which software architecture to use

19. Network Design Before looking inside a computer network, first agree on what a computer network is?

20. 20 Computer Network ? Set of serial lines to attach terminals to mainframe ? Telephone network carrying voice traffic ? Cable network to disseminate video signals ? Specialized to handle: Keystrokes Voice Video

21. 21 What Distinguishes a Computer Network ? Generality Built from general purpose programmable hardware Supports wide range of applications

22. 22 Applications – Users’ Contact with the Network Most people know the Internet through its applications –Web, email, streaming audio and video, chat, … Applications present an intuitively simple interface –Textual and graphical objects –Simple “clicks” to maneuver the application However, users are not aware of what happens in the network with their simple “clicks” !!!

23. 23 Applications – Consumers of Networks On a simple click, several messages may be exchanged over the Internet In a web browser, 17 messages may be exchanged –up to six messages to translate the server name –three messages to set up a TCP connection –four messages to send HTTP “get” request + response –four messages to tear down the TCP connection Moreover, millions of messages are exchanged each day by Internet nodes to make their presence and services known

24. 24 Applications – the Driving Force Streaming audio and video is an emerging application –Source generates and sends the video stream in messages across the Internet Video-on-demand: reads a preexisting movie –One-way data transfer Videoconferencing: interactive session –Very tight timing constraints Diversity of applications that can be built on top of the Internet hint at the complexity of the Internet design

25. 25 Our Road Map … Fortunately, we are not the first to build a computer network Lets start exploring the path that others have already dig deep By asking (and answering) why networks are designed the way they are

26. 26 Network Overview What must a network provide ? –Connectivity –Cost-effective sharing –Functionality –Performance How are networks designed and built ? –Layering –Protocols –Standards

27. 27 Perspective For network user –Connectivity: for services required; error free delivery within acceptable time limits For network designer –Efficiency: cost-effective design, fair allocation and efficient use of resources For network operator –Maintenance: easy to administer, fault localization & isolation, usage accounting

28. 28 Building Blocks Nodes: PC, special-purpose hardware… –Hosts –Switches Links: coax cable, optical fiber… –Point-to-point –Multiple access …

29. 29 Why not connect each node with every other node ? Number of computers that can be connected becomes very limited Number of wires coming out of each node becomes unmanageable Amount of physical hardware/devices required becomes very expensive Solution: indirect connectivity using intermediate data forwarding nodes

30. 30 Switched Networks –Two or more nodes connected by a link –Circular nodes (switches) implement the network –Squared nodes (hosts) use the network A network can be defined recursively as...

31. 31 Switched Networks –Two or more networks connected by one or more nodes: internetworks –Circular nodes (router or gateway) interconnects the networks –A cloud denotes “any type of independent network” A network can be defined recursively as...

32. 32 A Network A network can be defined recursively as Two or more nodes connected by a physical link OR Two or more networks connected by one or more nodes

33. 33 Components of a Network

34. 34 Switching Strategies Circuit switching: carry bit streams a.establishes a dedicated circuit b.links reserved for use by communication channel c.send/receive bit stream at constant rate d.example: original telephone network Packet switching: store- and-forward messages a.operates on discrete blocks of data b.utilizes resources dynamically according to traffic demand c.send/receive messages at variable rate d.example: Internet

35. 35 What next ? Hosts are directly or indirectly connected to each other Can we now provide host-host connectivity ? Nodes must be able to say which host it wants to communicate with

36. 36 Addressing and Routing Address: byte-string that identifies a node –Usually unique Routing: forwarding decisions –Process of determining how to forward messages to the destination node based on its address Types of addresses –unicast: node-specific –broadcast: all nodes on a network –multicast: some subset of nodes on a network

37. 37 Wrap-up A network can be constructed from nesting of networks An address is required for each node that is reachable on the network Address is used to route messages toward appropriate destination