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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] Sources marked as falseticker which shouldn't be
- From: Yuezhen LUAN <eggcar.luan@xxxxxxxxx>
- Date: Tue, 7 Jan 2025 17:33:05 +0800
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Thanks Miroslav, that explains the behavior, I'll try explain this to our SA.
We can solve this by increase the three server's dispersion to 10ms or larger
Miroslav Lichvar <mlichvar@xxxxxxxxxx> 于2025年1月7日周二 17:10写道：
>
> On Mon, Jan 06, 2025 at 06:12:53PM +0800, Yuezhen LUAN wrote:
> > But some of the chrony clients also mark B as falseticker, some marked B as
> > combined, some marked B as selectable but not combined, and all chrony
> > clients select C as current time source.
> >
> > Offset between B and C are small enough(currently 200us~300us). According
> > to selection algorithm, I think B shouldn't be falseticker? 'chronyc
> > selectdata -a -v' shows like this:
> >
> > [image: chronyc_selectdata.png]
>
> That output shows that the sources A and B don't have any overlap in
> their intervals and both overlap with C. This is a corner case in the
> chrony selection algorithm that IIRC is handled differently than in
> ntpd.
>
> That overlap between A and C is only about 30 microseconds. A small
> difference in the network delay, timestamping, etc could cause that
> overlap to disappear, which would make make B lose the falseticker
> status. That will also happen if A drifts further away from B and C.
>
> --
> Miroslav Lichvar
>
>
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