Round-trip delay
In
End-to-end delay is the length of time it takes for a signal to travel in one direction and is often approximated as half the RTT.
Protocol design
RTT is a measure of the amount of time taken for an entire message to be sent to a destination and for a reply to be sent back to the sender. The time to send the message to the destination in its entirety is known as the
Networks with both high bandwidth and a high RTT (and thus high bandwidth-delay product) can have large amounts of data in transit at any given time. Such long fat networks require a special protocol design.[3] One example is the TCP window scale option.
The RTT was originally estimated in TCP by:
where is constant weighting factor ().[4] Choosing a value for close to 1 makes the weighted average immune to changes that last a short time (e.g., a single segment that encounters long delay). Choosing a value for close to 0 makes the weighted average respond to changes in delay very quickly. This was improved by the
Wi-Fi
Accurate round-trip time measurements over Wi-Fi using IEEE 802.11mc are the basis for the Wi-Fi positioning system.
See also
References
- ^ Round-trip delay time, Boulder, Colorado: National Telecommunications and Information Administration's Institute for Telecommunication Sciences, archived from the original on 2021-10-17, retrieved 2021-05-29
- ISBN 9780072967753.
- Network World, archived from the originalon June 5, 2014, retrieved 2016-01-09
- ISBN 978-0-13-018380-4.