| Re: [chrony-users] chrony and ntpd xleave interoperability |
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On Wed, Jan 24, 2018 at 05:49:01PM +0100, Rob Janssen wrote:
> Miroslav Lichvar wrote:
> >
> > The bug in the interleaved mode is a bit more subtle. The state is
> > updated from received packet, but only when one of the timestamps is
> > zero (i.e. it's the first packet of the association). This means two
> > ntpd 4.2.8p10 can interoperate, but I suspect the association will not
> > recover if there is a mismatch between the receive timestamps.
> >
>
> I have seen problems like that, and stopped using symmetric peering.
> As far as I know, just declaring "server" in each direction works OK (there is loop-detection code)
> and appears a lot more stable. Probably and debugged tested better.
Yes, the complexity of the symmetric mode is ridiculous when compared
to the client/server mode.
As far as I know the only good use case for the symmetric mode is that
it can be used to push time to a server if it supports ephemeral
associations (chrony does not). I have some stratum-1 servers which
are behind NAT and their address is dynamic, and also some public
servers that are synchronized to them. If the public servers accepted
ephemeral assocations, they could be specified as peers on the
stratum-1 servers and it would work without forwarding ports on the
router and updating a DNS record with the dynamic IP.
--
Miroslav Lichvar
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