[ntp:questions] NTP offset doesn't change.

Rob nomail at example.com
Wed Feb 11 15:23:14 UTC 2015


Jochen Bern <Jochen.Bern at LINworks.de> wrote:
> However, I've also seen hardware occasionally flip-flopping from -900 to
> +1100 and back, complete with the developers of the firmware blaming "a
> bug in ntpd" for failure to discipline *that*.

Ok that is different, it is not a static drift.

But I see it has also been explained elsewhere in the thread: ntpd has
a maximum on the momentary drift of 500ppm, no matter if it is static
or dynamic or the sum of two.  I think that is not warranted.

There are also other problems with dealing with a variable drift.
I know from observations that ntpd does not attempt to handle a
changing drift, it only tries to lock in to the momentary drift and
when that is changing, it keeps chasing the drift (resulting in an offset).

In practice a changing drift is often caused by changing temperature,
and it would be better to take the first derivative into account as well.



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