David Mills wrote: > Bill, > > "Traditional" seems to imply some kind of voodoo art. See my 1997 > Internet survey which characterized the time and frequency errors of > some 27,000 NTP servers. The median error was 38.6 PPM, mean error 78.1 > PPM. 2.5 percent of the population showed zero error and 3 percent more > than 500 PPM error. Those two populations were not synchronized to a > working server. There is a histogram in the paper, which is also in my > book along with a discussion on the issues. Speaking for myself, in > probably several hundred machines I have seen at one time or another, > none had errors more than 200 PPM.
Someone should repeat the survey since that was 12 years ago. Clocks have changed but I suspect that the quality has not. > > The advice handed down in the documentation has always been to trim the > intrinsic error to less than 100 PPM by adjusting the tick value, either > with the tickadj program in the distribution or by some native OS > facility. Otherwise, the sawtooth error can become very large. > > Somebody should ask the question what happens in NTP if the intrinsic > error is greater than 500 PPM. Funny thing, the contraption keeps right > on working, but cannot trim the time offset to all the way to zero. What prevents the time offset from being trimmed to zero? Danny -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
