Data communication

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Data communication

  1. 1. Flow Control by Md.Javedul Ferdous East West University
  2. 2. Flow Control Flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with data from transmitting node.
  3. 3. So why need it ?????
  4. 4.  Prevent degradation and loss of efficiency due to overload.
  5. 5.  Prevent degradation and loss of efficiency due to overload.  Deadlock avoidance.
  6. 6.  Prevent degradation and loss of efficiency due to overload.  Deadlock avoidance.  Fair allocation of resources among competing users.
  7. 7.  Prevent degradation and loss of efficiency due to overload.  Deadlock avoidance.  Fair allocation of resources among competing users.  Speed matching between the network and its attached users.
  8. 8. Type of ‘Flow Control’  Stop-and-wait
  9. 9. Type of ‘Flow Control’  Stop-and-wait  Sliding Window
  10. 10. Stop-and-wait  Fundamental technique to provide reliable transfer under unreliable packet delivery system
  11. 11. Stop-and-wait  Fundamental technique to provide reliable transfer under unreliable packet delivery system  Simplest form of flow control
  12. 12. Stop-and-wait  Fundamental technique to provide reliable transfer under unreliable packet delivery system  Simplest form of flow control  Inefficiencies when sending longer transmissions
  13. 13. Stop-and-wait
  14. 14. Sliding Window  Technique for controlling transmitted data packets between two network computers where reliable and sequential delivery of data packets is required.
  15. 15. Sliding Window  Technique for controlling transmitted data packets between two network computers where reliable and sequential delivery of data packets is required.  Best utilized when the buffer size is limited and pre-established.
  16. 16. Sliding Window  Technique for controlling transmitted data packets between two network computers where reliable and sequential delivery of data packets is required.  Best utilized when the buffer size is limited and pre-established.  Better Performance.
  17. 17. Sliding Window
  18. 18. Levels of Flow Control  Hop Level
  19. 19. Levels of Flow Control  Hop Level  Entry-to-Exit Level
  20. 20. Levels of Flow Control  Hop Level  Entry-to-Exit Level  Network Access Level
  21. 21. Levels of Flow Control  Hop Level  Entry-to-Exit Level  Network Access Level  Transport Level
  22. 22. Hop Level  Prevent store and forward buffer congestion and its consequences
  23. 23. Hop Level  Prevent store and forward buffer congestion and its consequences  Maintain a smooth flow of traffic between two neighboring nodes In a computer network
  24. 24. Entry-to-Exit Level  Implement as a protocol between the source and destination switch
  25. 25. Entry-to-Exit Level  Implement as a protocol between the source and destination switch  Protect the exit node from congestion
  26. 26. Network Access Level  Throttle external inputs based on measurements of internal network congestion.
  27. 27. Transport Level  Efficient and reliable transmission of messages within each user session and the efficient sharing of common network resources by several user sessions
  28. 28. Transport Level  Efficient and reliable transmission of messages within each user session and the efficient sharing of common network resources by several user sessions  Events destination buffer congestion and overflow is known as transport level flow control
  29. 29. Problem of ‘Flow Control’ Can’t send too slow or too fast
  30. 30. Problem of ‘Flow Control’ Can’t send too slow or too fast Too slow
  31. 31. Problem of ‘Flow Control’ Can’t send too slow or too fast Too slow wastes time
  32. 32. Problem of ‘Flow Control’ Can’t send too slow or too fast Too slow wastes time Too fast
  33. 33. Problem of ‘Flow Control’ Can’t send too slow or too fast Too slow wastes time can lead to buffer overflow
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