Round-trip delay time

In telecommunications, the round-trip delay time (RTD) or round-trip time (RTT) is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgement of that signal to be received. This time delay includes the propagation times for the paths between the two communication endpoints. In telecommunications, the round-trip delay time (RTD) or round-trip time (RTT) is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgement of that signal to be received. This time delay includes the propagation times for the paths between the two communication endpoints. In the context of computer networks, the signal is generally a data packet, and the RTT is also known as the ping time. An internet user can determine the RTT by using the ping command. End-to-end delay is the length of time it takes for a signal to travel in one direction and is often approximated by half the RTT. Network links with both a high bandwidth and a high RTT (and thus high bandwidth-delay product) can have a very large amount of data 'in flight' at any given time. Such 'long fat pipes' require a special protocol design. One example is the TCP window scale option.