[ntp:questions] ntp-4.2.6p5 on Win 7 x64

Martin Burnicki martin.burnicki at meinberg.de
Fri Jul 25 10:15:51 UTC 2014


David Woolley wrote:
> On 24/07/14 11:21, Martin Burnicki wrote:
>> I'm assuming ntpd tries to synchronize the Windows time once every few
>> minutes
>
> I would expect it to be rather more frequent than that, as whilst the
> parameters might change only about once in seven or eight poll
> intervals, and the frequency may not change, the offset correction is
> applied in reducing increments so that there is only a finite integral,
> however long between updates.

I know, and if ntpd applies a "good" adjustment then Windows' tick 
adjustment is often updated once per second.

What I meant is that ntpd eventually *steps* the Windows time every few 
minutes, clears its filters, and starts from scratch.

Sorry for being imprecise.

Of setups where ntpd is unable to settle under Windows I've seen cases 
where ntpd then simply does nothing because the jitter is really much 
too large.

On the other hand there are cases where the system time is just stepped 
since an offset has been determined which exceeds 128 ms, and the game 
starts over from scratch every few minutes since the data collected from 
the next polls also provide very large jitter and offset.

Of course this happens only if timekeeping is broken as in the case 
discussed here.


Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany



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