"David J Taylor" <[email protected]> writes:
>Folks, >It's been suggested that if I have a mixture of a "known-good" (i.e. >GPS/PPS-based) LAN server, and some Internet-based backup servers, I could >use an ntp configuration file with different maxpolls, with the idea that >syncing more often to a good source will produce even lower offsets. >Something like: > server lan-gps-pps prefer iburst maxpoll 6 > server 0.uk.pool.ntp.org iburst > server 1.uk.pool.ntp.org iburst > server 2.uk.pool.ntp.org iburst >If I do this, is the maxpoll for the Internet servers also clamped at 6, >or will it gradually up to 1024s (10). No, not clamped. Maxpoll refers to the specific server it is referenced to . In your case lan-gps-pps. Because of the way ntp disciplines the clock, the disadvantage of low poll intervals is that the rate discipline of the clock is poorer. Now, if you remain attached to the source, that is not critical, since the more frequency polling makes up for it. But if you ever get disconnected from that source, your clock will drift off correct time faster. Actually your poll interval should be tuned to your particular computer's clock. If your computer receives a lot of variable use ( big high cpu programs for 15 min and then nothing for the next 15 min) poll 10 is too long. If it sits there chugging along doing exactly the same stuff all the time, It could even be too short. ntp has no way of measuring the real "Allan intercept" for your machine. chrony does that automatically, and as a result actually controlls the clock better than does ntp. But that is another topic. >Is this a sensible thing to do for a client without a refclock? It depends. Note that it also depends on who owns that refclock. They may not want people querying it so often. Certainly Mills would get annoyed if you clamped the poll interval to the udel servers at maxpoll 6 Of course if you own it, you can do as you wish. >Thanks, >David _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
