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Data Link Control

Data Link Control. ผศ. ดร. อนันต์ ผลเพิ่ม Asst. Prof. Anan Phonphoem, Ph.D. anan@cpe.ku.ac.th http://www.cpe.ku.ac.th/~anan Computer Engineering Department Kasetsart University, Bangkok, Thailand. Physical characteristics of interface Stream of Bits (e.g., 001010100100)

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Data Link Control

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  1. Data Link Control ผศ. ดร. อนันต์ ผลเพิ่ม Asst. Prof. Anan Phonphoem, Ph.D. anan@cpe.ku.ac.th http://www.cpe.ku.ac.th/~anan Computer Engineering Department Kasetsart University, Bangkok, Thailand

  2. Physical characteristics of interface • Stream of Bits (e.g., 001010100100) • Line config. (e.g., point-to-point) • Topology (e.g., bus, star) • Transmission mode • (e.g., half-duplex, full-duplex) • Encoding • Error detection (and correction) Application 5 4 Transport 3 Network 2 Data Link 1 Physical TCP/IP Protocol Suite

  3. Application 5 4 Transport 3 Network 2 Data Link • Line Discipline • Flow Control • Error Control 1 Physical TCP/IP Protocol Suite

  4. Who Should send data and When ? How much data may be sent? How can errors be Detected and correct? Data Link Control Line Discipline Flow Control Error Control

  5. Data Link Control ENQ / ACK LineDiscipline Poll / Select Flow Control Error Control

  6. Line Discipline: ENQ/ACK Peer-to-peer communication

  7. Line Discipline: ENQ/ACK

  8. Line Discipline:Poll/Select Primary-secondary communication Multipoint Discipline

  9. Select

  10. Poll

  11. Data Link Control Line Discipline a set of procedures used to restrict the amount of data that the sender can send Stop-and-wait (one frame at a time) Flow Control Sliding window (several frames at a time) Error Control

  12. Stop-and-wait

  13. Sliding window

  14. Sender sliding window

  15. Receiver sliding window

  16. Example of sliding window

  17. Control variable

  18. Example of sliding window

  19. Data Link Control Line Discipline Flow Control Stop-and-wait ARQ Error Control • Sliding window ARQ • Go-back-n • Selective-reject

  20. Stop-and-wait ARQ: Normal Operation

  21. Stop-and-wait ARQ: Damaged frame

  22. Stop-and-wait ARQ: Lost data frame

  23. Stop-and-wait ARQ: Lost ACK frame

  24. Stop-and-wait ARQ: Delay ACK

  25. Stop-and-wait ARQ: Piggybacking

  26. Sliding WindowGo-back-n: Normal Operation

  27. Sliding WindowGo-back-n: Damaged data frame

  28. Sliding Window Go-back-n: Lost Data Frame

  29. Sliding Window Go-back-n: Lost ACK

  30. Sliding Window Selective-reject: Damaged data frame

  31. Sliding window ARQ Comparison • Go-back-n • Simple • More practical • Selective-reject • Complex (sorting, storage, extra select frame logic) • Better performance

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