Text book: Data and Computer Communications William Stallings

1. Text book:Data and Computer CommunicationsWilliam Stallings Reference Books: 1- computer networkes,Andrew S.Tanenbaum 2- Data Communications and Networking, 3rd Edition, Behrouz A. Forouzan

2. Chapter 1 Introduction to networking

3. What is the computer network

4. Network • Aset of devices (nodes) connected by communication links. • A node can be a • Computer • Printer, or • Any other device capable of sending and/or receiving data generated by other nodes on the network.

5. Why StudyData Communication & Networking? • Because Data Communication & Networking are changing the way we do business and the way we live • Require immediate access to accurate information • Database, online shopping • Enable long distance communication • Internet, IP phone • Access variable of information such as text, voice and image • Email, messenger, video conference

6. What is Data Communication? • Communications • The exchange of information between individuals using a common set of symbols, signs, behavior or language. • Data • Information presented in whatever forms is agreed upon by the parties creating and using data • Datacommunications • The exchange of data between two devices via some form of transmission medium such as a wire cable

7. 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

8. Simplified Communications Model - Diagram

9. A Data Communication Model • Message • Sender • Receiver • Medium • Protocol

10. Simplified Network Model

11. 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

12. Simplified Data Communications Model

13. 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

14. TYPE OF CONNECTION • Point to point • A dedicated link is provided between two devices • Multipoint • More than two specific devices share a single link Point – to – point connection Multipoint connection

15. Broadcast Networks • Types of transmission technology • Broadcast links • Point-to-point links

16. Distributed Processing A task is divided among multiple computers

17. Broadcast Networks (2) • Classification of interconnected processors by scale.

18. Network Criteria • Performance – affected by • # users • Type of medium • HW/SW • Reliability – measured by • Freq of failure • Recovery time • Catastrophe vulnerability • Security • Protection from unauthorized access • Viruses {Homework; difference between virus & worm}

19. Categories of Networks • Based on • Ownership • Distance covered • Physical architecture • Control

20. Network Hardware • Local Area Networks • Metropolitan Area Networks • Wide Area Networks • Wireless Networks • Home Networks • Internetworks

21. Internetworks • Connection of two or more networks • Internet vs. internet • internet • Two or more networks can communicate with each other • Internet • A collaboration of more than hundreds of thousands interconnected networks

22. The Internet • Collaboration of more than hundreds of thousands of interconnected networks • 1969 – started as ARPAnet, a small network of connected computers • 1972 - Cerf and Khan – packet delivery and Transmission Control Protocol (TCP) • Shortly thereafter – evolution of TCP/IP

23. Wide Area Networks • 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)

24. Local Area Networks • 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

25. Metropolitan Area Networks • A metropolitan area network based on cable TV.

26. Wireless Networks • Categories of wireless networks: • System interconnection • Wireless LANs • Wireless WANs

27. Wireless Networks (2) • (a) Bluetooth configuration • (b) Wireless LAN

28. Wireless Networks (3) • (a) Individual mobile computers • (b) A flying LAN

29. Wireless LANs • (a) Wireless networking with a base station. • (b) Ad hoc networking.

30. Wireless LANs (2) • The range of a single radio may not cover the entire system.

31. Wide Area Networks • Relation between hosts on LANs and the subnet.

32. Circuit Switching • Dedicated communications path established for the duration of the conversation • e.g. telephone network

33. 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

34. 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

35. 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

36. 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

37. Asynchronous Transfer Mode • ATM • 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

38. Protocols and Standards • Why do we need them? • Protocol • set of rules that govern data communication • defines what, how, and when • Key elements • Syntax • Semantics • timing • Standard • provides a model for development • allows for interoperability

39. OSI Model • Open Systems Interconnection • Developed by the International Organization for Standardization (ISO) • Seven layers • A theoretical system delivered too late! • TCP/IP is the de facto standard

40. 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

41. Key Elements of a Protocol • Syntax • Data formats • Signal levels • Semantics • Control information • Error handling • Timing • Speed matching • Sequencing