[ntp:questions] Loop Frequency and Offset

Miroslav Lichvar mlichvar at redhat.com
Tue Sep 27 11:12:36 UTC 2011

On Tue, Sep 27, 2011 at 10:20:57AM +0100, David Woolley wrote:
> Richard B. Gilbert wrote:
> >
> >I don't believe that accuracy of 1 microsecond , or less, is
> >obtainable without without installing a GPS Timing Receiver or an
> >atomic clock of some sort.
> He asked for an offset of 1 microsecond (presumably RMS or 90
> percentile?), not an accuracy of 1 microsecond.
> If you ignore systematic errors, an offset of 1 microsecond
> corresponds to an accuracy in the low 100s of nanoseconds.

Only if the loop is tracking frequency changes well. If you see in
the loopstats log long runs of offsets with the same sing, the actual
error is probably closer to the reported offset.

Miroslav Lichvar

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