[ntp:questions] LOCL clock reachability not 377?

Martin Burnicki martin.burnicki at meinberg.de
Thu Jul 31 08:31:10 UTC 2014


William Unruh wrote:
> Ie, once ATOM has been selected, it should remain selected, unless it
> also gets switched of for a few hours, or there is a disagreement
> between ATOM and some other selected clock source by more than a second.

On the other hand, if the PPS signal is bound to a certain time source 
and that time source starts freewheeling the 1 PPS signal also starts to 
drift, and that may *not* be what you want.

If I remember correctly we had a discussion here quite some time ago 
where ntpd enabled kernel PPS when a GPS receiver+PPS was synchronized, 
but didn't disable kernel PPS when the GPS receiver lost its input 
signal. The PPS from the GPS receiver started to drift away and also 
pulled the kernel time away.

So as usually it always depends on some preconditions, i.e. if the PPS 
signal is still reliable in case the associated prefered peer goes away, 
or not.


Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany



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