[ntp:questions] Tighter regulation?

Steve Kostecke kostecke at ntp.org
Tue May 21 14:24:27 UTC 2013

On 2013-05-21, Mischanko, Edward T <Edward.Mischanko at arcelormittal.com> wrote:

> My concern is that too much data is being thrown away when polling
> above 256 seconds and that allows excessive wandering of my clock.

The clock filter algorithm processes the offset and delay samples
produced by the on-wire protocol for each peer process separately. It
uses a sliding window of eight samples and picks out the sample with the
least expected error.

http://www.eecis.udel.edu/~mills/ntp/html/filter.html describes
the algorithm design principles along with an example of typical

> Yes, I can cap the interval to 256, but is that the only answer?
> I would rather increase the interval of adjustments not the polling
> interval. 

A general overview of the clock discpline algorithm; along with
discussions of phase-lock loop operations, loop dynamics, and clock
initialization and management; are presented at

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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