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Computer and Data Communications

Computer and Data Communications. output data. input data. transmitted signal. received signal. input information. Transmission medium. Input device. Output Devices. Transmiter. Receiver. A Communications Model. output information. information : The meaning that

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Computer and Data Communications

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  1. Computer and Data Communications

  2. output data input data transmitted signal received signal input information Transmission medium Input device Output Devices Transmiter Receiver A Communications Model output information information : The meaning that is currently assigned to data by means of the conventions applied to those data data : A represent of facts , concepts in a formalized manner suitable for communication

  3. Data Communication Network Communication Network Node Network Station Communication Network

  4. Data communication networks • Public Switched Telephone Network (PSTN) • Local Area Network (LAN) • Leased lines • Public switched data network (PSDN) • Integrated services digital network (ISDN)

  5. PSTN • modem link via PSTN PSTN modem modem

  6. hub hub hub hub LAN station 4th floor • confined geographical area • under single management • high data rate station 3rd floor station 2nd floor 1st floor server router

  7. LAN Voice Leased lines • Lease pubic circuits to connect different sites • Communication channel is privated LAN leased circuit Voice LAN Voice

  8. PSDN • PSDN is designed specifically for the transmission of data rather than voice • Comunication is shared LAN PSDN= Public Switched Data Network LAN PSDN = LAN

  9. ISDN Using ISDN to carry both voice and data NTE = Network termination equipment NTE NTE ISDN = Integrated services digital network ISDN NTE NTE

  10. Computer A Computer B File transfer application File transfer application Communications service module Communications service module Network access module Network access module Computer Communication Architecture File and file transfer command Communication-related messages Network interface Communication network

  11. Applications Transport Network access Three-layers model

  12. Applications 1 2 3 4 ( ) ( ) ( ) ( ) Transport Network access Communication architectures and networks Applications Service Access Point 1 2 ( ) ( ) Transport Network Address Network access Communication network Applications 1 2 3 ( ) ( ) ( ) Transport Network access

  13. Computer A Computer B Application Application Transport Transport Network access Network access Protocol layers Application protocol Transport protocol Network Access Protocol Computer B

  14. Protocol data unit Application data Transport protocol data unit (TPDU) Transport header Application data Transport header Application data Network protocol data unit (NPDU) Network header Transport header Application data Network header Transport header Application data • control info + data in each layer = protocol data unit (PDU)

  15. OSI reference Model Layer 7 Application layer • developed by ISO Layer 6 Presentation layer Layer 5 Session layer Layer 4 Transport layer Layer 3 Network layer Layer 2 Data link layer Layer 1 Physical link

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