On Tue, Jan 18, 2011 at 07:18:08PM +0000, unruh wrote: > On 2011-01-18, David Woolley <david@ex.djwhome.demon.invalid> wrote: > > The actual error, when locked, should be almost an order of magnitude > > less than the typical offsets. Moreover, if there is both jitter and > > Uh, it depends. If the frequecy shifts ( more or less work being done by > the computer) ntp will track very badly. Anyway, if the errors are > random, many measurement over a short period will keep the accuracy > better than the same number of measurements over a long period. And be > more responsive to frequecy shifts. Also ntpd's averaging time is NOT of > the order of 100 poll intervals ( which you would need to get your order > of magnitude) Especially as ntpd uses only one of every 8 polls, the > actual statistical improvement is less than 3, not an order of > magnitude.
It seems to depend on the distribution of network delays too. With normally distributed delays I see improvement about 3, but with exponentially distributed delays it's slightly more than 10. Is that because the selected sample is the one with the best delay, so it carries more information than the others? -- Miroslav Lichvar _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
