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Sliding Window with cumulative ACK: ACK frame lost

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• Sliding Window Example: ACK Error - case 1: not the last ACK

  • Sliding Window operation when an ACK frame (not the last one) is corrupted:

    Sender: Send window = [0, 1, 2] Receiver: Receive window = [0, 1, 2] Example: ACK 2 is lost

    Notes:

    ACK 2 was lost When the sender receives ACK 3: ACK 3 will also acknowledge data frame 1 !!! ACK 3 will acknowledge the data frame 2 !!! It's like receiving ACK 2 again !!! (Here you can see the ACK protection mechanism of cumulative ACK in action !!!!)

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• Sliding Window Example: ACK Error - case 2: the last ACK is lost
  • Sliding Window operation when an last ACK frame is lost:

    Sender: Send window = [0, 1, 2] Receiver: Receive window = [0, 1, 2] Example:

    Explanation:

    When the last ACK is lost, the sender will time out and retransmit the last data frame (The last ACK is not protected by an later ACK !!!)