[ntp:questions] Odd (mis)behavior when reference clock fails

Steve Kostecke kostecke at ntp.org
Tue Sep 23 16:07:44 UTC 2008


On 2008-09-23, Kevin Oberman <oberman at es.net> wrote:

> [---=| Quote block shrinked by t-prot: 40 lines snipped |=---]
>
>> It would be helpful to know the exact NTP version, and which hardware clock
>> and refclock driver was used.
>
> It's 4.2.4p4 running on FreeBSD 7.0. The reference clock is a EndRun
> Tech CDMA clock using the TrueTime driver. When the system was running,
> ntpq claimed no successful polls of the reference clock or the PPS. It
> was getting good responses from other systems, but not syncing to
> them.

The ntpq peer billboard you posted shows that ntpd _has_ chosen another
system as the sys_peer. See below.

> The offset started small after the clock failed, about .003, and
> steadily grew to over 5 ms. The reference clock always showed a zero
> reachability, delay and offset and .001 jitter.

ntpd has not received any data from the ref-clock. That's one problem.
You may want to check the CDMA clock to make sure that it is actually
working.

The increasing drift is another issue.

> Here is the ntpq -p output after restoring the reference clock to the
> config and letting it run for a few minutes. Drift is already
> significant!
> # ntpq -p
>      remote           refid      st t when poll reach   delay   offset  jitter
>==============================================================================
>  TRUETIME(1)     .CDMA.           0 l    -   16    0    0.000    0.000   0.001
>  PPS(1)          .PPS.            0 l    -   16    0    0.000    0.000   0.001
> -time1-owamp.es. .PPS.            1 u   17   64  177    2.058  -10.335   0.038
> *time2-owamp.es. .PPS.            1 u   49   64  177   24.556  -10.408   0.020
> -time3-owamp.es. .PPS.            1 u   63   64  176   55.640  -10.337   0.049
> +time4-owamp.es. .PPS.            1 u   59   64  176   20.770  -10.405   0.058

Is there something about this system which is different from the other
time servers?

-- 
Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/




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