"Richard B. Gilbert" <rgilber...@comcast.net> writes: >Evandro Menezes wrote: >> It's not so much a question of clock error as the ability of NTP >> converging too slowly. If it could slew by more than 500PPM, than it >> could even avoid time steps, especially backwards. >> >> It seems that being able to slew more than 500PPM is what makes Chrony >> perform so much better than NTP in adverse conditions. >> >> I'm starting to wonder if NTP actually stands for "standard (normal) >> temperature and pressure", to hint at its ideal conditions >> design... :-)
>The design was intended to cope with the horrors of the internet. >Packets may arrive with variable delays. Some may not arrive at all. >Ntpd does manage to extract a reasonable approximation of the correct >time in spite of having to do it over the internet. You might find it >interesting/useful to look at the statistics for ntpd during the period >11PM to 7AM local time and compare them with the stats for the other >sixteen hours of the day. >If you find that chrony gives you better results, please feel free to >use it. I had thought that this discussion group was a group to discuss time on computers using the ntp protocol, including improvements in the way that the reference implimentation uses the protocol to discipline the clocks. The evidence is that at least under some fairly broad circumstances, chrony disciplines the clocks better than does the reference implimentation ( by factors reported to be from 2 to 20 times better), converges to the correct time far faster than does ntp, does not step the time, and can handle out of spec clocks ( eg whose drift rate is larger than 500PPM) better. I would think that this might lead the reference implimentation to consider altering its approach so that it at least equaled chrony. It may of course be that there are circumstances where ntp does better, but noone has ever demonstrated that as far as I know, and if it is true, it would be really useful to know. But the discussion strikes me as being similar to the discussion between the American and Japanese car makers in the 90s. Time and again, it was argued that the Japanse were better than the American in all kinds of areas, and the response of the American car makers was "If they are so much better why don't you just go buy one". And eventually the Americans did. At the same time I see statements that chrony controlled clocks should not be allowed as part of the pool, and that there are ways of determining that they are not runnning reference ntp and thus could be actively kept out of the pool. Reminds me of the attempts by the American car makers to have the government outlaw Japanese cars. chrony does have weaknesses. It runs only on Linux and BSD at present. It has a much smaller range of refclocks that it supports ( as of now only the shm refclock added very recently by Lichvar). Both are distinct disadvantages. What I would like to see is a dispassionate examination of the strengths and weaknesses of the various approaches, and have the reference implimentation use the very best. Instead I see what looks like a religion, where questions are treated as apostasy or treason. (You remember the statements to the Vietnam protestors, that if they do not like everything the US does, they should move to Russia, or Vietnam, or Liberia, or....) _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
