David Woolley wrote: > David J Taylor wrote: > >> >> Neither, directly. I mean the peak-to-peak variation in the reported >> offset, as "measured" by eye on a graph like the "Daily" graph here: > > For a Millsian network, the peak to peak value would be unbounded, so > one needs to consider RMS, or assume a non-Millsian constraint, such > as bounded peak to peak measurement error. > > Thinking more about it, I think there will be no nett effect from the > measurement error, so the only contribution will be from oscillator > frequency. It looks like that is assumed to vary as the square root > of poll interval. > > So, I would say, for small poll intervals, asymptotic to constant and > for large poll intervals, asymptotic to the 1.5th power) of the > interval. ntpd attempts not to choose poll intervals that take it > beyond the transition between these two, so maybe sub-linear for all > of the normal operation range. If you get something significantly > different, you may not have a Millsian network, and ntpd may not be > the right tool for you. > > If you want the real answer, you will need to ask Dave Mills, but he > will probably just point you to his mathematical analysis, and I > suspect you are asking here because you don't feel competent to use > those, or rich enough to buy the book.
David, A figure of the 1.5th power is fine for me. As I only have two "by eye" measurements, I can neither say that's right or wrong. It's certainly not inconsistent. The book is on my Amazon wanted list, but I'm not sure how much I will appreciate if it's mainly maths. One of my criteria for judging image processing papers was "doe it contain images?"! Thanks, David _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions