[ntp:questions] Jitter versus polling interval
david at ex.djwhome.demon.co.uk.invalid
Sun Mar 1 10:23:39 UTC 2009
David J Taylor wrote:
> Does anyone know an approximate relationship between polling interval
> and peak-to-peak jitter for a non-ref-clock system? I.e would the
> jitter offset) go up linearly with polling interval, or as the square,
> or what?
Do you mean true jitter (RMS error from true time) or the jitter
statistic produced by NTP?
I may be completely wrong, but I thought that true jitter initially went
down with increasing polling interval and that ntpd stopped increasing
the polling interval before it started to go back up again. That's
because ntpd increases the loop time constant as it increases, which
compensates for the increased poll interval and, in the Millsian world,
measurement jitter has a 1/f spectrum.
In the real world, you'll need to specify the nature of the measurement
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