[ntp:questions] Strange jumps in PPM
david at ex.djwhome.demon.invalid
Thu Aug 22 21:24:45 UTC 2013
On 22/08/13 19:02, unruh wrote:
> ntpd assumes that the source is perfect. It has not choice. It does
> assume that network delays etc can make the measurements inaccurate, and
I was contrasting it with the fact that it is rather reluctant to accept
that the local clock has wandered off, compared with assuming that there
is wander on the measurements of the upstream.
> tried to get rid of those by averaging, and filtering. (throwing away
> 87% of the emasurements) which makes its response slow. But it assumes
No. They make it over-sample. The poll rate is adjusted so that 1 in 8
samples gives updates faster than needed for its estimate of the optimum
> that the sources are perfect without other evidence (eg disagreement
> between sources).
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