[ntp:questions] Synchronize clocks without a reference clock

Maarten Wiltink maarten at kittensandcats.net
Mon Mar 19 11:21:33 UTC 2007

"Spoon" <devnull at localhost.com> wrote in message
news:45fe6248$0$27199$426a74cc at news.free.fr...
> Maarten Wiltink wrote:
> When you say that the clock in a server next to a door will wander a
> lot, are you referring to the effects of the sudden temperature swing
> when a cold draft comes in the server room?


>> The other potential problem is that there is a maximum drift that can
>> be corrected. If the difference between your server and any other host
>> is larger than that, the client won't be able to follow the server,
>> while both would be able to follow UTC. This is unlikely but possible.
> I was wondering whether it is possible to reduce the maximum rate of
> change? Is that what the tinker dispersion option is for?
> http://www.ee.udel.edu/~mills/ntp/html/miscopt.html
> "The argument becomes the new value for the dispersion increase rate,
> normally .000015 s/s."
> Does this mean that the maximum rate of change is 15 µs per second?

No, that's something else, probably the worst-case estimate for how
fast synchronisation deteriorates between server polls. But that's no
more than a guess.

The number I mean is the 500PPM cap on the observed drift that NTP will
accept before giving up. You can't change that without recompiling, IIAMN.

Maarten Wiltink

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