[ntp:questions] Re: Slew mode check for NTP (Windows)

Paul.Croome at softwareag.com Paul.Croome at softwareag.com
Fri Jul 28 08:15:16 UTC 2006


Sasikumar Jayaraman schrieb:

> Say, i start the NTP service as "ntpd -x" and change the system time 3
> minutes ahead of clock source.
>
> How much time it will take to correct the time?

The maximum slew rate is 500ppm, therefore an error of 1 second is
corrected
in ~2000 seconds and an error of 180 seconds is corrected in ~360,000
seconds
-- that's a tad over 4 days.

This is documented in
http://www.eecis.udel.edu/~mills/ntp/html/ntpd.html#op.
See the paragraph beginning "The issues should be carefully
explored..."

I'll say it again: NTP is really not designed to be run in environments
where
the time suddenly twiches by several minutes. It does a great job when
its
external time references advance at a uniform rate that's close to 1
second per second.

Paul




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