Howard Barina wrote: > > Does an NTP servers take into account it's estimated offset in serving time
There seem to have been a lot of questions asked in the last month that are based on the false assumption that "offset" measures the difference between the local clock and true time. Has someone published a misleading document, somewhere? > to others? If I am a server and think I am 1.5 milliseconds off from true > time, will I include this in the timestamps of my ntp replies to others? An NTP client never thinks that its time is wrong. If it did, it would be admitting that the NTP algorithms are wrong. Therefore the server always serves its client's idea of the time. The "offset" should always be within the statistical error from the current measurement history (if ntpd suspects otherwise, it steps, and/or reduces the poll interval, to try to rapidly re-acquire that condition). Immediately after startup, there will be little history, so quite large offsets will still be consistent with that history. There are people who who argue that the NTP algorithms are fundamentally flawed and don't give the statistically best time in real world situations. I think they have some credibility, but NTP's inventor, does not. However, what one can certainly say is that combining "offset" with the local clock is very unlikely to give you a better time than just using the local time at all times except immediately after startup or after significant upsets. "offset" is the difference between the clients best estimate of the true time and a weighted average of the most recent "best" measurements from its upstream servers. Those measurements have a significant measurement error. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
