[ntp:questions] Single best NTP status indicator of clock accuracy?
David Woolley
david at ex.djwhome.demon.invalid
Fri Dec 11 07:49:04 UTC 2009
unruh wrote:
>
> Offset. That is ntp's best guess as to the difference between the time
> on your clock and the true UTC time. ntp keeps no record of the rate
No. It is the difference between the time on your clock and the last
measurement from other clocks. It includes the instantaneous
measurement error, but not systematic measurement error. When ntpd is
operating in a stable environment and locked onto its sources, the
instantaneous offset readings can vary widely and the RMS value will be
quite a bit larger than the RMS variation in error in the actual machine
clock.
The big argument is about how often ntpd is actually operating in a
stable environment. When it is out of lock, offset approximates the
short term part of the error, but still does not include the systematic
error.
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