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Comprehensive Course on Computer Networks and Data Communications

This course aims to provide students with an understanding of the fundamental principles of computer networks, including an exploration of the Internet and its protocols. Students will learn to describe the operations of Internet protocols, develop their own applications, and gain knowledge on data communications, local area networks (LAN), and wide area networks (WAN). The curriculum includes lectures, two examinations, and hands-on reports to reinforce learning. Key textbooks include "Data and Computer Communications" by William Stallings and "Computer Networks" by Andrew S. Tanenbaum.

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Comprehensive Course on Computer Networks and Data Communications

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  1. Computer Networks 2003/Fall Division of Electronics & Information Engineering Chonbuk University

  2. Course Syllabus (I) • Lecturer : Gihwan Cho • office : room 607 (voice 3437) • email : ghcho@dcs.chonbuk.ac.kr • office hour : Tue. 11:00 ~ 13:00 or by appointment • Teaching assistant : Ilsik Yang • office : Distributed Computing System Lab. (room 618) • email : isyang@dcs.chonbuk.ac.kr • office hour : Tue: 11:00 ~ 13:00, Wed. 10:00 ~ 11:00 • Text Books • W. Stallings, Data & Computer Communications, 6th edition, Prentice Hall, ISBN 0-13-086388-2 • Andrew S. Tannenbaum, Computer Networks, 3rd edition, Prentice Hall, ISBN 0-13-349945-6

  3. Course Syllabus (II) • Course objectives • understanding of the basic principles of computer networks • understand the Internet and its protocols • then, you are expected to be able to • describe in detail the operations of Internet protocols • develop your own Internet applications • Outline • overall introduction of data & computer communications • data communications • wide area networks • local area networks • communications architecture and protocols

  4. Course Syllabus (III) • Expected works • 2 examinations (mid, final), 2 reports (problems in exercise) • Lecture information • WilliamStallings.com/DCC6e.html • dcs.chonbuk.ac.kr/~ghcho/courses/comnet.html • Grading • exam. 70(35, 35), reports 20(10, 10), attendance 10 • students are not majored in CS will be separately evaluated from those of majored in CS

  5. Lecture Topic I Overall Introduction

  6. Chapter 1 : A Communications Model • Source • generates data to be transmitted • Transmitter • converts data into transmittable signals • Transmission System • carries data • Receiver • converts received signal into data • Destination • takes incoming data

  7. Simplified Communications Model : Diagram Destination System Source System Trans- mission System Trans- mitter Source Source Receiver Destination (a) General block diagram Workstation Modem Modem Server Public Telephone Network (b) Example

  8. Key Communications Tasks • Transmission system utilization • Interfacing • Signal generation • Synchronization • Exchange management • Error detection and correction • Addressing and routing • Recovery • Message formatting • Security • Network management

  9. Digital bit Stream Analog signal Digital bit Stream Analog signal Text Text Trans- mission System Trans- mitter Receiver Destination Source Input Information m Input data g(t) Transmitted signal g(t) Received signal r(t) Output data g’(t) Output information m’ Simplified Data Communications Model

  10. Why Data Networking • Point to point communication not usually practical • devices are too far apart • large set of devices would need impractical number of connections • Solution is a communications network

  11. Switching node Wide-area network Source System Destination System Trans- mission System Trans- mitter Source Receiver Destination Local area network Simplified Network Model

  12. Wide Area Networks (WAN) • Large geographical area • Crossing public rights of way • Rely in part on common carrier circuits • Alternative technologies • circuit switching • packet switching • frame relay • Asynchronous Transfer Mode (ATM)

  13. Circuit Switching, Packet Switching • Circuit switching • dedicated communications path established for the duration of the conversation • e.g. telephone network • Packet switching • data sent out of sequence • small chunks (packets) of data at a time • packets passed from node to node between source and destination • used for terminal to computer and computer to computer communications

  14. Frame Relay, ATM • Frame relay • packet switching systems have large overheads to compensate for errors • modern systems are more reliable • errors can be caught in end system • most overhead for error control is stripped out • ATM (Asynchronous Transfer Mode) • evolution of frame relay • little overhead for error control • fixed packet (called cell) length • anything from 10Mbps to Gbps • constant data rate using packet switching technique

  15. Local Area Networks (LAN) • Smaller scope • building or small campus • Usually owned by same organization as attached devices • Data rates much higher • Usually broadcast systems • Now some switched systems and ATM are being introduced

  16. Protocols • Used for communications between entities in a system • Must speak the same language • Entities • user applications • e-mail facilities • terminals • Systems • computer • terminal • remote sensor

  17. Key Elements of a Protocol • Syntax • data formats • signal levels • Semantics • control information • error handling • Timing • speed matching • sequencing

  18. Protocol Architecture • Task of communication broken up into modules • For example file transfer could use three modules • file transfer application • communication service module • network access module

  19. A Simplified Three Layer Model • Network access layer • exchange of data between the computer and the network • sending computer provides address of destination • may invoke levels of service • dependent on type of network used (LAN, packet switched etc.) • Transport layer • reliable data exchange • independent of network being used • independent of application • Application layer • support for different user applications • e.g. e-mail, file transfer

  20. Addressing Requirements • Two levels of addressing required • Each computer needs unique network address • Each application on a (multi-tasking) computer needs a unique address within the computer • the service access point or SAP

  21. Protocol Architectures and Networks

  22. Protocol Data Units (PDU) • At each layer, protocols are used to communicate • Control information is added to user data at each layer • Transport PDU • transport layer may fragment user data • each fragment has a transport header added • destination SAP • sequence number • error detection code • Network PDU • adds network header • network address for destination computer • facilities requests

  23. Operation of a Protocol Architecture

  24. TCP/IP Protocol Architecture • Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) • Used by the global Internet • No official model but a working one • application layer • host to host or transport layer • internet layer • network access layer • physical layer

  25. TCP/IP Protocol Architecture Model

  26. OSI Model • Open Systems Interconnection • Developed by the International Organization for Standardization (ISO) • Seven layers • application • presentation • session • transport • network • data Link • physical • A theoretical system delivered too late! • Currently, TCP/IP is the de facto standard

  27. OSI v TCP/IP

  28. Standards • Required to allow for interoperability between equipment • Advantages • ensures a large market for equipment and software • allows products from different vendors to communicate • Disadvantages • freeze technology • may be multiple standards for the same thing • Web sites for IETF, IEEE, ITU-T, ISO

  29. Standardization (I)

  30. Standardization (II)

  31. Standardization (III)

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