[ntp:questions] Stabilizing the drift file?

Juergen.Salm at siemens.com Juergen.Salm at siemens.com
Fri Nov 24 14:36:09 UTC 2006

Hi Dave.

> This could be avoided by forcefully setting the clock at initial
> startup

That's exactly what we do.

You have to know that Robert an I are working on the same project.
Robert is a systems engineer of the platform we use to build our

The requirements of max. 100ms external offset, max. 10ms internal
offset an 5 minutes until service availability are coming from our
requirement specification. ;-)
And we are always talking about a reboot scenario. So we don't need to
compensate large offsets.

What we do now during reboot is
a) Measure the drift with my script for 2 seconds
b) Set the time with ntpdate -b
c) start ntpd with "iburst burst minpoll 4 maxpoll 6" for the
controller blades requiring  <100ms offfset and with "iburst burst
minpoll 4 maxpoll 4" for those blades requiring <10ms among themselves

So ntpd can start its operation with (almost) no initial offset and a
drift that is +-2ppm away from the long-term value.
This gives us a max. offset of <<1 ms right from the start.
And that's what we were looking for. :-)


More information about the questions mailing list