In telecommunications, the term round-trip delay time or round-trip time (RTT) is the time it takes for a segment to sent and the time it takes for an acknowledgement of that segment to be received. One problem that TCP must figure out is how to deal with timeouts and retransmissions. Round-trip delay time or Round-trip time is a big factor in helping to decide when to do both. RTT may also be used to find the best possible route.

In the context of computer networks, the signal is generally a data packet, and the time is also known as ping time. An internet user can determine RTT by using the ping command.