In telecommunications, the term round-trip delay time or round-trip time (RTT) has the following meanings: 1. * The elapsed time for transit of a signal over a closed circuit, or time elapsed for a message to a remote place and back again. 2. * In primary or secondary radar systems, the time required for a transmitted pulse to reach a target and for the echo or transponder reply to return to the receiver. In regards to TCP communication the RTT time is calculated from the 3-way handshake by measuring the time between segment transmission and ACK receipt.