Spoon wrote: > Keith E. Brandt, M.D. wrote: > >> /home/brandt 53> ntpq -p >> remote refid st t when poll reach delay >> offset jitter >> ============================================================================== >> >> >> *GPS_NMEA(0) .GPS. 0 l 2 64 377 0.000 >> 0.005 0.017 >> -ntp.your.org 130.126.24.44 3 u 47 64 377 62.065 >> 4.289 2.750 >> +boudicca.tux.or 65.212.71.102 2 u 12 64 377 63.289 >> -5.525 2.273 >> -dake.desynched. 132.163.4.103 2 u 18 64 377 55.516 >> 4.039 2.726 >> -veritas.imagepi 67.128.71.76 2 u 60 64 377 51.816 >> -8.385 2.495 >> -hudson.yutanigl 128.252.19.1 2 u 20 64 377 50.768 >> -5.847 14.944 >> +ferocious.dairi 140.142.16.34 2 u 18 64 377 119.579 >> -0.465 11.587 >> >> 'Poll' is the polling interval in seconds, which seems to vary quite a >> bit on my system, so here's the first real question - how does ntp >> pick the polling interval (a pointer to the docs is fine, I just >> haven't been able to uncover it yet). > > > Have you played with minpoll and maxpoll? > > http://www.eecis.udel.edu/~mills/ntp/html/confopt.html > > minpoll minpoll > maxpoll maxpoll > > These options specify the minimum and maximum poll intervals for NTP > messages, in seconds as a power of two. The maximum poll interval > defaults to 10 (1,024 s), but can be increased by the maxpoll option to > an upper limit of 17 (36.4 h). The minimum poll interval defaults to 6 > (64 s), but can be decreased by the minpoll option to a lower limit of 4 > (16 s). These option are valid only with the server and peer commands. > > I don't know under what conditions ntpd changes the polling interval.
Playing with MINPOLL and MAXPOLL is NOT recommended!! Ntpd varies the polling interval between MINPOLL and MAXPOLL in order to best respond to existing conditions. The math is over my head but it has something to do with the "Allan Intercept" q.v. My oversimplified English explanation is that short polling intervals allow large errors to be corrected quickly while the longest polling interval allows small errors to be corrected very accurately. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
