Q & A on Timing out a TCP connection Q: I have been looking through Volume 1 & 2 on the topics of TCP timeouts. I have been looking in the section on "Timeout And Retransmission" where you talk about round trip times. My question to you would be what would make a TCP connection timeout? Is there a certain number of retries that need to happen before a timeout? A: TCP does not define a maximum number of retransmissions before giving up. However, it does define a maximum segment lifetime, and assumes that no response within two maximum segment lifetimes indicates a hopeless situation. Thus, if one attempts to communicate with a machine that is down, TCP will give up after retransmitting for about 5 minutes.