[ntp:questions] NMEA ref.clock better than my ISP's timeserver?

David Lord snews at lordynet.org
Thu Jun 11 15:57:34 UTC 2009

David J Taylor wrote:
> David Lord wrote:
> []
> With my broadband, I recall that PCs kept well within +/- 100ms, but I 
> perhaps have a different usage pattern to you.  I like the idea of a 
> buffered PPS feed to each server, and would be most interested to hear 
> how it works out.  To be within a few ms though, having one stratum-1 
> server and the rest over the LAN would probably be adequate.  BTW: I'm 
> using different minpoll and maxpoll values to have the benefit of both 
> LAN stratum-1 and Internet fallback servers, without hammering the 
> Internet servers too hard.
> ____________________________________
> server  iburst maxpoll 6  prefer # startum-1
> server  maxpoll 6  # second stratum-1
> server 0.uk.pool.ntp.org minpoll 10
> server 1.uk.pool.ntp.org minpoll 10
> ____________________________________

Similar here for remotes, minpoll 9, maxpoll 11 and all currently
sat at 2048 sec. I have five servers in each list though.

I only have a pair of servers as peer and that is maxpoll 8 and
both sat at 256 sec. Offsets are 203us and 593us.

I have problems with the larger maxpoll value as temperature
changes are sometimes at a higher rate than ntpd can compensate
for but this affects the pcs differently and having peers with
lower maxpoll might help. Otherwise the higher maxpoll does
seem to tend to give lower offset variation and jitter. So far
this year I've not had temperature in back room shoot from 15C
to near 30C as happened on a couple of days last year.


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