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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