[ntp:questions] Re: Box not synchronizing
Richard B. Gilbert
rgilbert88 at comcast.net
Fri Jun 9 21:52:00 UTC 2006
John Pettitt wrote:
> 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
Yup! Another factor is that hardware refclocks do not have the jitter
problems that network servers do. You can use a much shorter poll
interval with a good refclock.
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