[ntp:questions] Slow convergence of NTP with GPS/PPS

David J Taylor david-taylor at blueyonder.neither-this-part.nor-this-bit.co.uk
Fri Oct 24 14:56:21 UTC 2008

Richard B. Gilbert wrote:
> Try it some time!  Ntpd makes a mad dash for zero offset, overshoots,
> and then "rings" for a while.  Eventually it gets that tight synch
> that we like to see but it does take about thirty minutes.
> I think I mentioned this here at the time I observed it.  I believe
> that I also remarked that I could have done it a lot faster by hand
> if I had the "control knobs".

Looking at the behaviour of client PCs synching to a GPS-stratum-1 server, 
what you say surprises me somewhat.  The initial transient seems to die 
out very rapidly, judged on a "50ms" scale.  That's with a Windows client 
as well.  As the stratum-1 server has a much better reference, and as the 
poll is fixed at 64s, I would have thought that 5ms was no problem at all. 
Just feed the PPS signal to all the clients.

Oh, well.


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