[ntp:questions] Single best NTP status indicator of clock accuracy?

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Fri Dec 11 03:28:48 UTC 2009


unruh wrote:
> On 2009-12-10, kjans <kert.jans at gmail.com> wrote:
>>   I am looking for the best single indicator that can be used to
>>   determine/monitor the current clock accuracy.
> Offset. That is ntp's best guess as to the difference
>  between the time on your clock and the true UTC time.

AFAICT

ntpq -c rv gets the system variables, among them is a combined
 offset (ms) from the selected truechimer peers reference times,
 (or the offset from the preferred peer).
 e.g. ntpq -c rv ... offset=-5.515 ...

ntpdc -c loopinfo will also get that offset in a different format.
 e.g. ntpdc -c loopinfo offset:               -0.005515 s ...


The Root Dispersion to the primary reference clock (stratum 1),
 would be "the difference between the time on your clock and
 the true UTC time" (ms)
 e.g. ntpq -c rv ... rootdisp=56.621 ...
  {with GPS/PPS, root dispersion will likely be 5. or less.}


<http://alumni.media.mit.edu/~nelson/research/ntp-survey99/html/>
"dispersion of that root time: these measurements are useful
  for determining the final accuracy of a host's clock"

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