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

David Lord snews at lordynet.org
Tue Apr 13 09:14:31 UTC 2010

lhommedumatch wrote:
> 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
>>> fudge stratum 10
>>> Then:
>>> service ntpd stop
>>> ntpdate ntpgmtaceb
>>> 12 Apr 21:46:22 ntpdate[9860]: adjust time server 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

I have 4.2.0-r which doesn't support the options I mentioned,
4.2.4p2-o here has some of them and other options have been
added for more recent versions.


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