[ntp:questions] Re: NTP, no external time source, peering "Undisciplined Local Clocks" ?

Maarten Wiltink maarten at kittensandcats.net
Wed Oct 19 11:15:03 UTC 2005

"Marco Molteni" <mmolteni at cisco.com> wrote in message
news:200510181619.11961.mmolteni at cisco.com...
> I know I can tell NTP to use the local clock as a time reference, what
> is called an "Undisciplined Local Clock" in the NTP documentation.
> Say I don't know if a clock is better than the other, so by configuring
> B and C to use A as server I risk to have a not so good time if A is
> unreliable.
> Can I configure A,B,C to peer with each other in a meshed fashion, so
> to have each clock influenced by all the others?

Even if two clocks more or less agree on the time and the third one is
an outlyer, there would be no reason to believe that the two agreeing
ones are more right.

In order for the local clock to work as a reference clock, NTP has
to _believe_ it. And it will effectively believe that it's exactly
accurate, with zero offset and zero jitter. By definition. So NTP has
no basis to judge the "quality" of the clocks on, anymore than you do.

Maarten Wiltink

More information about the questions mailing list