[ntp:questions] What exactly does "Maximum Distance Exceded" mean?
david at ex.djwhome.demon.co.uk.invalid
Fri Mar 13 22:41:03 UTC 2009
Joseph Gwinn wrote:
> In article <49ba0e33$0$505$5a6aecb4 at news.aaisp.net.uk>,
> David Woolley <david at ex.djwhome.demon.co.uk.invalid> wrote:
>> Joseph Gwinn wrote:
>>> What is this error likely telling me? What are the possibilities? What
>>> tests will tell the tale?
>> Your timeservers are unsynchronised, but for some reason not setting
>> their stratum to 16.
>> Distance exceeded means that the combination of worst case round trip
>> time induced error and an assumed drift of 15ppm since the last valid
>> time on the root server (plus a few minor components) has exceeded 1 second.
> How would it know of drift, in this isolated little island?
What is described here is not what is conventionally called an island.
An island is a system which does not and never has had a source of
ntpd doesn't care about what the drift is in determining root distance.
It simply takes the position that the actual local clock will be
somewhere within +/- 15ppm of the value which would achieve perfect
phase lock with true time.
The assumed maximum reasonable error therefore grows at 15 microseconds
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