[ntp:questions] Re: Box not synchronizing

John Pettitt jpp at cloudview.com
Fri Jun 9 20:25:20 UTC 2006


Brian Utterback wrote:
> 
> So, there you have it. I hope that helps you to understand how
> a longer poll interval can lead to a more accurate clock, and
> why it is a good idea to let NTP decide what the best poll interval
> actually is.
> 
>

Great explanation - it also explains why sometime you do need to mess with minpoll and maxpoll.  If
you have a machine that is prone to rapid changes in it's drift rate (typically due to thermal
issues) when ntp moves to a longer poll it doesn't notice fast enough that the clock is drifting
faster or slower that it was before.  This is very visible with PC based stratum 1 clocks where
sporadic system loads (causing heat in the cpu) can push the clock off by hundreds of microseconds
before ntp catches it and brings it back.  Setting minpoll and maxpoll to 4 for the refclock source
can significantly improve the systems ability to remain relatively stable through these thermal events.

john




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