[ntp:questions] how to have offset < 1ms

lhommedumatch ludocluba at yahoo.com
Tue Apr 13 08:05:26 UTC 2010


On 13 avr, 00:44, David Lord <sn... at lordynet.org> wrote:
> lhommedumatch wrote:
> > I'm working on a oceanographic vessel
> > ntpgmtaceb is our reference clock that is synchronised with a gps at
> > the beginning of a cruise.
> > The drift of this clock is <1ms each day.
> > It's connected on the lan board of our vessel.
>
> > I have removed these two lines
> > server 127.127.1.0
> > fudge   127.127.1.0 stratum 10
>
> > Then:
> > service ntpd stop
> > ntpdate ntpgmtaceb
> > 12 Apr 21:46:22 ntpdate[9860]: adjust time server 192.168.21.5 offset
> > -0.000252
> > sec
>
> > service ntp start
>
> > ntpq -p
> >      remote           refid      st t when poll reach   delay
> > offset  jitter
> > ==============================================================================
> > *ntpgmtaceb      .1PPS.           1 u   20   64  377    0.144
> > -0.373   0.863
>
> > So it's seems to be really better, isn't it?
>
> Delay on that connection is 0.144 vs 29.431 your original message
> so it's probably "better" because of that rather than removal of
> LOCAL(0). If original figure from delay was correct, eg due to
> network load, then you'd need to get that fixed.
>
> If using a recent ntpd you can have "tos orphan 10" to fallback
> to local clock if it's sufficiently reliable, and other tos
> options to set limits on what time if any is accepted and reported.
>
> What version of ntpd are you running?
>
> David

I'm using ntpd 4.2.2p1




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