[ntp:questions] Change poll interval at runtime?

David J Taylor david-taylor at blueyonder.co.uk.invalid
Sun Feb 26 18:20:36 UTC 2012


"A C" <agcarver+ntp at acarver.net> wrote in message 
news:4F4A6E79.3010707 at acarver.net...
[]
> It's the latest dev version on NetBSD using five network servers plus 
> the SHM refclock plus the ATOM refclock.  The SHM is not very stable 
> with its offset so I don't use it right now which leaves me ATOM plus 
> network (one of the network servers is marked prefer).  (Don't ask about 
> using NMEA with PPS enabled, it doesn't work due to the serial drivers 
> on NetBSD/sparc so PPS has to be separate via a second serial port).
>
> If I set minpoll to 8 or 9 to be nice to the network servers, it takes 
> six or eight polling periods before ATOM turns on and becomes the system 
> peer.  If I leave out minpoll, ATOM clamps the polling period to 64 
> seconds.  It still takes six to eight polling periods to activate ATOM 
> but 8 * 64 is much less than 8 * 256 or 8 * 512.

Thanks for that summary, there are so many systems being discussed that 
it's easy to lose touch!

Leaving aside the question of when the ATOM driver becomes selected, isn't 
the time accurate enough for your purposes simply by using the five 
networks servers within a minute or two?  I take it that you have "iburst" 
against all the servers, and that you have one of them marked "prefer"? 
Can you accept a reduced accuracy until the ATOM kicks in?

In the discussions I had with Dave Mills here some time back, I recall 
that it was a requirement that is the ref clock was at 16s intervals, the 
Internet servers shouldn't be at 1024s, although that does seem to work 
correctly here.  I have at the back of my mind a feeling that it's tied in 
with the NMEA not working, i.e. the ATOM driver is somehow working on its 
own (as an edge of second reference) without a "time of day" source being 
polled at a similar interval.

Anyway, all I can suggest is trying FreeBSD and seeing whether its serial 
drivers will work for you.  I don't feel I can help further.

Cheers,
David 



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