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Relationship between Receive buffers and Send buffers

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• The relationship between send buffer size and receive buffer size
  • Rule for correctness:

    # outstanding data frame ≤ send buffer size

    because otherwise, the sender may not be able to re-transmit some lost frame (because that data frame was not buffered)

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    Best setting:

    # outstanding data frame = send buffer size

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  • Rule to achieve better efficiency (i.e.: minimal wastage):

    # outstanding data frames ≤ receive buffer size Or: send buffer size ≤ receive buffer size

  • Reason:

    If receive buffer size < # outstanding frames, then some correctly received data frames can be discarded (= lost): Then: These discarded frames must be re-transmitted later !! Inefficient use of transmission capacity !!!

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• Setting used to achieve the best performance
  • Setting used at the sender for optimal efficiency:

    send buffer size = # outstanding frames

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  • Setting used at the receiver for optimal efficiency:

    receive buffer size = send buffer size