[ntp:questions] Re: Windows - Seven Days Later

Jerry Baker jerry at novalid.invalid
Wed Oct 13 12:59:17 UTC 2004

David Woolley wrote:
> You seem to be have been taking a very hostile attitude to ntpd all along,
> but you have been continually changing the goalposts and dribbling in
> critical pieces of information.  What, for example, happened to your
> original 2.6s step problem?

I don't think it's hostile. NTP, after all, is a software package and I 
don't think software can experience "hostility." The reason I suspect 
NTP is because most of the people involved with NTP seem to be pretty 
hostile towards Windows in general, and completely unwilling to even 
entertain the notion of exploring possible work-arounds for this issue. 
Most responses are something like, "uh, well, I don't have Windows but I 
think it works like this."

> Looking at your MRTG graphs, you are not getting uni-directional clock
> steps, but rather paired forward and backward steps, which are slightly
> confused because the clock never appears stable enough for ntpd to
> establish a large poll interval and long time constant, so ntpd has
> partially corrected the step in one direction, before the counter step
> (note, as I pointed out before, the phase errors are the cause of the
> frequency changes, not the other way round).  ntpd is doing its best
> with low quality time data that keeps stepping backwards and forwards
> by what looks like a clock tick.

The poll interval has remained 1024s for two weeks.

> How are you instrumenting the SNTP client?  In any case, most SNTP clients
> use relatively long poll intervals, which will tend to low pass filter
> out the forwards and backwards steps in the time measurment.  You may be
> able to make ntpd filter them out by using a longer minpoll, but I can't
> guarantee that that won't result in instability or a failure of the loop
> to initally capture.

I set up an SNTP client (D4) to poll every 15 minutes. When I do that it 
shows a regular correction of about 5ms.

> Of course, if you really think that ntpd is broken on NT, the source is
> published and you can debug it yourself.  The NT specific code ought to
> be fairly easy to find.

I hope your mechanic never says, "well, I'm not going to fix your car, 
but if you think something is wrong there's all the parts."

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