"David Woolley" <[email protected]> wrote in message news:[email protected]... [] > 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: enable stats statsdir "C:\Tools\NTP\etc\" statistics loopstats 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. http://www.satsignal.eu/mrtg/daily_ntp.html It puzzles me somewhat why the same ntpd.exe running on Windows-XP (Feenix) 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 PC. Cheers, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
