[ntp:questions] Re: [Bug 177] Clock stepping messes up frequency. (fwd)

David L. Mills mills at udel.edu
Wed Nov 12 06:36:48 UTC 2003


Not true, but close. The clustering algorithm is much more sneaky than
you assume. The metric decisions are intricate and probably boring to
others on this list, but there is firm principle involved. Take a look
at the architecture briefing at the NTP project page. I warmly welcome
discussion on the principles therein. The selection and clustering
algorithms have a twenty year history, but I would be thrilled to adjust
them in view of modern experience.


David J Taylor wrote:
> > I guess I need to poke at the old ntp research papers a bit more.  I
> > can't believe I'm the first person to notice this.
> >
> > -wolfgang
> > --
> > Wolfgang S. Rupprecht      http://www.wsrcc.com/wolfgang/
> >            The From: address is valid.  Don't mess with it.
> Wolfgang (and others),
> My observation is that given an equal set of e.g. stratum 2 servers, NTP
> will select the one with the greatest delay if the jitter from the servers
> is similar.  This results in, for example, a server in a different
> continent (170ms delay) being preferred over one that is much more local
> (40ms delay).  I believe this is a similar effect to the one that you
> reported.  Like you I prefer not to use the prefer qualifier.
> Cheers,
> David

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