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

unruh unruh at wormhole.physics.ubc.ca
Mon Apr 12 22:48:30 UTC 2010

On 2010-04-12, lhommedumatch <ludocluba at yahoo.com> 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.

Why not put a Garmin GPS 18  on board the ship and get gps time on the
whole cruise?

But why are you getting 20ms roundtrip delay going from one onboard
computer to that computer. the ship is only say 100m long, which is at
best 1usec delay ( yes, I knwo the delay is dominated by the
switches/hubs along the way).

> 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

That doe slook a lot better. I am not sure why the delay should be so
much different however. 

> So it's seems to be really better, isn't it?

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