[ntp:questions] high precision tracking: trying to understand sudden jumps

David Woolley david at ex.djwhome.demon.co.uk.invalid
Sun Mar 30 23:30:37 UTC 2008

Maarten Wiltink wrote:
> You seem to be missing the point. Once the large errors have been
> corrected, NTP goes on to the small errors. For that, it _needs_ a
> longer poll interval. That this gives the server more air is a
> happy coincidence, but not why it does it.

I don't believe it *needs* longer poll intervals; I think they are 
simply wasteful in that the offsets are low pass filtered in such a way 
that clamping maxpoll makes very little difference to the result, when 
the time constant goes high.

I'm not sure that there is any user configurable option that actually 
does what people think they are doing by locking down maxpoll, in terms 
of keeping the loop time constant low.

A clamped maxpoll may improve the reponsiveness to faults causing time 
steps of more than 128ms, but one should be attacking the problem, not 
the symptom.

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