Round-trip delay time
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In telecommunications, the term round-trip delay time or round-trip time (RTT) has the following meanings:
- 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.
- 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.
Round-trip delay time is significant in systems that require two-way interactive communication, such as voice telephony, or ACK/NAK data systems where the round-trip time directly affects the throughput rate, such as the Transmission Control Protocol. It may range from a very few microseconds for a short line-of-sight (LOS) radio system to many seconds for a multiple-link circuit with one or more satellite links involved. This includes the node delays as well as the media transit time.
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