2.20 TCP Timeouts

Animation 2.20-1 shows the TCP acknowledgement, timeout and retransmission.

The last TCP byte reaching the receiver had the sequence number 30. Thus, the receiver's acknowledgement number will be 31. This value identifies the number of the next byte which is to be sent by the other side. After receiving this acknowledement the sender transmits the next bytes numbered for example 31 to 60. Assuming that the sender does not receive the next acknowledgement with the number 61 within a certain time interval it retransmits the bytes 31-60.