[ntp:questions] 500ppm - is it too small?
David J Taylor
david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Thu May 7 16:12:46 UTC 2009
I've recent been suggesting the Windows port of NTP as a program suitable
for an application where the timekeeping needed to be within a second or
two. Yes, NTP is overkill, but it has the advantages of multiple servers,
best server selection, adaptive poll rate, and memory of the clock drift
etc. However, on quite a few installations - at a guess between 1% and
5% - NTP has failed because the click frequency error appears to be too
great for NTP to correct.
Is there any feeling for changing the 500ppm limit, perhaps to 1000ppm or
even as much as 5000ppm (to pull a figure out of the hat)? Or is 500ppm
generally believed to be the worst error which should be compensated?
One possibility is that some of the problem PCs are portables, with some
sort of power-saving or even hibernation scheme. I don't have direct
visibility of the type of PC.
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