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4123702 Data Communications System

4123702 Data Communications System. By Ajarn Preecha Pangsuban. Part 1 Overview of Data Communications and Networking. Chapter 1 Brief description of data communication, networking, and protocol standards Chapter 2 Network models. Chapter 1 - Introduction. Data Communication.

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4123702 Data Communications System

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  1. 4123702Data Communications System By Ajarn Preecha Pangsuban

  2. Part 1Overview of Data Communications and Networking • Chapter 1 • Brief description of data communication, networking, and protocol standards • Chapter 2 • Network models 4123702 Data Communications System @YRU

  3. Chapter 1 - Introduction

  4. Data Communication • Why study data communications? • Data communication is the exchange of data between two devices via a transmission medium • Effectiveness depends on: • Delivery • Accuracy • Timeliness 4123702 Data Communications System @YRU

  5. Communication System Components 4123702 Data Communications System @YRU

  6. Data Representation • Text – represented as a bit pattern, a sequence of bit (0s or 1s); codes often used: • ASCII; Extended ASCII; Unicode; ISO • Numbers – represented by binary equivalent • Images – bit patterns representing pixels • Audio • Video 4123702 Data Communications System @YRU

  7. A Communications Model DTE: Data Terminal Equipment DCE: Data communication Equipment 4123702 Data Communications System @YRU

  8. Simplified Communications Model 4123702 Data Communications System @YRU

  9. Simplified Data Communications Model 4123702 Data Communications System @YRU

  10. Simplified Network Model 4123702 Data Communications System @YRU

  11. Direction of Data Flow • Simplex – unidirectional; one transmits, other receives 4123702 Data Communications System @YRU

  12. Direction of Data Flow (cont) • Half-duplex – each can transmit/receive; communication must alternate 4123702 Data Communications System @YRU

  13. Direction of Data Flow (cont) • Full-duplex – both can transmit/receive simultaneously 4123702 Data Communications System @YRU

  14. Networks • A network isset of devices (nodes) connected by communication links (media) • A node can be a computer,printer,or other device capable of sending and/or receiving data • Link connecting the devices are often called communication channels • Most network use distributed processing • Advantages? 4123702 Data Communications System @YRU

  15. Network Criteria (Standard) • Performance – depends on number of users, type of medium, HW/SW • Reliability – measured by freq of failure, recovery time, catastrophe vulnerability • Security – protection from unauthorized access, viruses/worms 4123702 Data Communications System @YRU

  16. Types of Connections • Point-to-point – dedicated link 4123702 Data Communications System @YRU

  17. Types of Connections (cont) • Multipoint (Multidrop) – shared a single link 4123702 Data Communications System @YRU

  18. Physical Topology • The way in which a network is laid out physically • 4 basic types: mesh, star, bus, ring • May often see hybrid 4123702 Data Communications System @YRU

  19. Mesh Topology • Dedicated point-to-point links to every other device • Has n(n-1)/2 physical channel to link n devices • Devices have n-1 I/O • Advantages? • Disadvantages? 4123702 Data Communications System @YRU

  20. Star Topology • Dedicated point-to-point links to central controller (hub) • Controller acts as exchange • Advantages ? • Disadvantages ? 4123702 Data Communications System @YRU

  21. Bus Topology • Multipoint configuration • One cable acts as a backbone to link all devices • Advantages ? • Disadvantages ? 4123702 Data Communications System @YRU

  22. Ring Topology • Dedicated point-to-point configuration to neighbors • Signal is passed from device to device until it reaches destination • Each device functions as a repeater • Advantages ? • Disadvantages? 4123702 Data Communications System @YRU

  23. Categories of Networks • LAN – smaller geographical area • WAN – large geographical area 4123702 Data Communications System @YRU

  24. Local Area Network • Usually privately owned and links the devices in a single office, building, or campus • LAN size is limited to a few kilometers. • LANs are designed to allow resources to be shared (hardware , software and data ) • Today LANs to have data rates of 100 Mbps to 10Gbps • Backbone Networks (BN), have a scale of a few hundred meters to a few kilometers. Include a high speed backbone linking the LANs at various locations. 4123702 Data Communications System @YRU

  25. Figure 1-2 Local Area Network (cont) 4123702 Data Communications System @YRU

  26. Figure 1-2 Local Area Network (cont) 4123702 Data Communications System @YRU

  27. Wide Area Network • WAN provides long distance transmission of data, voice, image, and video information over large geographical areas • Comprise a country, a continent, or even the whole world (Interlink age of many LANs and MANs) • Low data transmission rate (below 1 Mbps) • Unlimited number of miles example: Internet Network 4123702 Data Communications System @YRU

  28. Figure 1-4 Wide Area Network (cont) 4123702 Data Communications System @YRU

  29. Internetworks • Connection of two or more networks by the use of internetworking devices which include routers and gateways • Internet is a generic term used to mean an interconnection of networks • The Internet is the name of a specific worldwide network. 4123702 Data Communications System @YRU

  30. Figure 1-5 Internetworks (cont) 4123702 Data Communications System @YRU

  31. The Internet • Collaboration of more than hundreds of thousands 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 4123702 Data Communications System @YRU

  32. The Internet today 4123702 Data Communications System @YRU

  33. Protocols and Standards • Why do we need them? • A protocol is a set of rules that governs data communication; the key elements of a protocol are • Syntax – data formats and Signal levels • Semantics – control information and error handling • Timing – speed matching and sequencing • Standards are necessary to ensure that products from different manufacturers can work together as expected. 4123702 Data Communications System @YRU

  34. Standards • Types – • De jure (Formal) – legislated by an officially recognized body • De facto – by convention or widespread use • Standards Organizations • Committees – ISO, ITU-T, ANSI, IEEE, and EIA • Forums – special-interest groups that quickly evaluate and standardize new technologies • regulatory agencies – FCC • Internet Standards • Drafts (6 month lifetime) • RFC is an idea or concept that is a precursor to an Internet standard. 4123702 Data Communications System @YRU

  35. Credits • All figures obtained from publisher-provided instructor downloads Data Communications and Networking, 3rd edition by Behrouz A. Forouzan. McGraw Hill Publishing, 2004 4123702 Data Communications System @YRU

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