[ntp:questions] Odd (mis)behavior when reference clock fails
oberman at es.net
Tue Sep 23 18:25:43 UTC 2008
> From: Steve Kostecke <kostecke at ntp.org>
> Date: 23 Sep 2008 16:07:44 GMT
> Sender: questions-bounces+oberman=es.net at lists.ntp.org
> 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.
Yes, that is quite clear.
> > 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
It is NOT working. That is what started this whole thing. The clock
failed and time started drifting even though it had lots of peers with
working clocks. (The system in question is about 5000 kilometers away
from me.) Except for the time drift, ntp seemed to be working fine. It
just is not drifting the systems time and I don't understand why.
> 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?
As stated, all of the servers are identical in terms of hardware and
software and configuration. The only differences in the ntp.conf is that
each system is missing the entry for itself.
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
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