[ntp:questions] Win2k3 Server as NTP server?
David J Taylor
david-taylor at blueyonder.not-this-bit.nor-this-part.co.uk.invalid
Mon Dec 7 08:47:18 UTC 2009
"David Woolley" <david at ex.djwhome.demon.invalid> wrote in message
news:hfiddi$qc4$1 at news.eternal-september.org...
> I think he was really asking about the parameters that you log and how
> you get them from ntpd.
> He is using ntpq to fetch the "offset" value. If ntpd is working well,
> this will be noise like and centred around zero. Under those
> circumstances, its jitter should be several times worse than the true
> jitter in the software clock. Windows applications' idea of th time
> will be compromised by the limitations of Windows, in particular its
> inability to interpolate between ticks, There may also be a systematic
> error due to network limitations, etc.
> If the offset is not noise like, the offset may be close to the actual
> clock error, as ntpd has poor transient response to things like
> temperature changes.
I hope the answer is covered in the Web pages to which I pointed, but if
not, I use ntpq to get offset and sometimes jitter, and I enable the
statistics logging with lines in the ntp.conf such as:
The files can be read by both Meinberg's and my own plotting programs.
I find that the offset is far from noise-like on some systems (Feenix and
Narvik, both running XP), reflecting the temperature or rate of change of
temperature. On other systems it is more noise-like (PCs Stamsund and
Hydra) and the loopstats averaged jitter on those systems is Hydra 1ms and
Stamsund 25us. Hydra is a Windows 7 system with LAN sync, and Stamsund a
Windows-7 system with a GPS/PPS local reference.
It puzzles me somewhat why the same ntpd.exe running on Windows-XP
has a much worse /apparent/ offset than one running under Windows-7. Both
PCs have a GPS/PPS reference, 16s poll, and both behaved similarly under
Windows-XP. In Windows-7, the interpolation scheme is disabled, which
seems to result in a much lower average offset, but with an increased
noise on the plots. The Windows-XP machine shows an averaged jitter in
the loopstats of 2.5us, compared to 25us for the un-interpolated Windows-7
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