[ntp:questions] Re: tinker step 0 (always slew) and kernel time discipline

Richard B. Gilbert rgilbert88 at comcast.net
Fri Sep 22 21:35:20 UTC 2006

David Woolley wrote:

> In article <ef19v5$kqn$1 at zcars129.ca.nortel.com>,
> Joe Harvell <harvell at nortel.com> wrote:
>>This actually happened in a testbed for our application. NTP stats show
> * that over the course of 22 days, the offsets of two configured NTP
> * servers (both ours) serving one of our NTP clients started diverging
> * up to a maximum distance of 800 seconds.  During this time, our NTP
> This could only happen if either the implementation was broken, or
> they were mis-using the local clock pseudo reference clock.  If the
> servers were using a proper reference clock as their primary source,
> root dispersion would have exceeded it's maximum value when the
> error was probably a lot less than a second and the servers would have
> been rejected completely.

This just what happened.  Both servers seem to have been serving their 
unsynchronized local clocks.  The servers diverged and the client had no 
way to judge which one was more nearly correct.  If the configuration 
was not designed to fail, it certainly was left prone to failure of just 
the sort that actually happened.

He would have been better off not using NTP at all!  The clock might not 
have been accurate but it would never have stepped.

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