[ntp:questions] Re: Small fixed offset

Martin Burnicki martin.burnicki at meinberg.de
Fri Oct 28 10:58:33 UTC 2005

ariel.burbaickij at gmail.com wrote:

> There is misunderstanding here.
> The signals are timestamped at the equipement after they are feed in
> into it.
> In order to get accurate timestamps (where by accurate I mean time as
> the
> signals where seen/generated in USA not as signals were feed in into
> equipment in Central Europe) we have to introduce small offset on the
> clocks
> on the equipment (they must run 150 milliseconds behind the real time)
> . It is not
> possible to timestamp signals in USA as the backhauling equipement is
> not much more than optical fibre cables.  Clocks
> are synchronized from private ntp server. I am not talking about
> compensating
> the network latency in NTP protocol itself. Is it more clear now?

AFAIK you can only fudge the time offset of NTP refclocks, not the offset of
external NTP servers since that wouldn't make much sense under the aspects
of NTP policy.

>From my point of view a proper solution was not to fudge the local system
time of your equipment, but add an offset to the time stamps which are
taken in the equipment. 

You should also keep in mind that the network delay may vary over time, so
you might use the delay value of the ntpq -p output to determine the actual
delay and subtract that from the time stamps you've taken from your
correctly synchronized local clock.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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