[ntp:questions] Choice of local reference clock seems to affect synchronization on a leaf node

Dave Hart hart at ntp.org
Wed Nov 9 03:27:23 UTC 2011


On Wed, Nov 9, 2011 at 03:12, Nathan Kitchen
<nkitchen at aristanetworks.com> wrote:
> On Tue, Nov 8, 2011 at 6:59 PM, Dave Hart <hart at ntp.org> wrote:
>> I agree that I would not expect to see any difference in behavior
>> between LAN source only (#1) and LAN source + orphan mode (#2).  I am
>> not surprised to see difference in behavior with 4.2.6 between either
>> of those and using a LAN source and the LOCAL driver (#3) as that
>> version is prone to switch to the LOCAL driver more often than is
>> helpful.  If you stick with that version of ntpd, I would advise
>> avoiding the LOCAL driver, and I would also wonder if even orphan mode
>> is helpful in this case.  Why not use config #1, what problem is LOCAL
>> or orphan mode solving?
>
> It doesn't exactly solve a problem, but faster synchronization is nice
> to have, and it does appear to have that effect.

In the case of LAN source + orphan mode, what is the refid reported by
ntpq immediately after the faster synchronization?  If it is
127.0.0.1, the sync is illusory, as it's really self-synced.
Referring to:

http://doc.ntp.org/4.2.6p1/miscopt.html#tos

I see 4.2.6p1 does not have "tos orphanwait" at all, so orphan mode
will be entered immediately after the big clock step, but only
temporarily until enough samples come in from the network source for
it to be selectable.  FYI, current 4.2.7 extends orphanwait to also
hold off selection of backup reference clocks such as LOCAL and ACTS
modem to give other sources a chance and avoid transient clock
hopping.

> Thanks for the insight on the appropriate use of LOCAL and orphan mode.

You're welcome.

Cheers,
Dave Hart


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