NTPD unable to adjust local clock

Joerg Sonnenberger joerg at britannica.bec.de
Thu Apr 7 00:27:22 PDT 2005

On Wed, Apr 06, 2005 at 10:36:23AM -0700, Matthew Dillon wrote:
>     First, we have to do away with ntpd's code that tries to take the
>     average from multiple time sources.  What a disaster that is!  At
>     the very *best* we can have a heuristic based on the offsets from
>     each source to try to correct the offsets, but otherwise we have to
>     choose the best time source (lowest standard deviation at the lowest
>     stratum) and stick with it.  None of this averaging between sources
>     business.  Each time source has to be independantly tracked and we
>     pick the best one, period.

Just to get the fact right, it does *not* average the time sources, it
uses the median of all good peers. Using the stratum doesn't make much sense,
because e.g. all major German time servers are stratum 2 or greater, even
if they have a Caesium watch at the same institute to synchronise too or a
long wave reciever for the "official" time signal. You don't know which
the *current* best source is, but you can try to choose a good source. That's
done. I'll have to dig into xntp, but I'd be surprised if it did something else.


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