Network Analysis Using Wireshark 2 Cookbook - Second Edition

TCP selective acknowledgement

In the previous sections, we discussed how the TCP sequence number and acknowledgment number help provide reliability to the end application. But the default acknowledgement and the retransmission behavior are not throughput efficient due to the nature of TCP requiring to retransmit all the segments from the missing segment within the sliding window. The following is an illustration that helps us understand the default behavior better.

For illustration, we are using a TCP session with window size of five segments. Based on the window size, the Sender can send five segments before waiting for the acknowledgement. ...