Here are the stat/charts I've been taking pulling for a month. Well really I've been doing it for over 6/months, but I restarted my data about a month ago.vThe average is around 1-5/µs over a month.
Millisecond (ms) Offset: http://godzilla.empire.org/ntp.html Microsecond (µs) Offset: http://godzilla.empire.org/ntpv2.html godzilla# ntpq -c rv assID=0 status=04fd leap_none, sync_uhf_clock, 15 events, event_13, version="ntpd [email protected] Mon Feb 20 22:00:33 UTC 2012 (1)", processor="amd64", system="FreeBSD/9.0-RELEASE-p3", leap=00, stratum=1, precision=-19, rootdelay=0.000, rootdisp=0.312, refid=PPS, reftime=d3d59e76.89ae1a0d Wed, Aug 15 2012 0:05:10.537, clock=d3d59e7a.e70eae83 Wed, Aug 15 2012 0:05:14.902, peer=34072, tc=4, mintc=3, offset=0.014, frequency=-24.202, sys_jitter=0.005, clk_jitter=0.000, clk_wander=0.000 godzilla# Thanks to David Taylor's MRTG configs and perl scripts ( http://www.satsignal.eu/ntp/NTPandMRTG.html) On Tue, Aug 14, 2012 at 6:08 PM, Andreas Krüger <[email protected]>wrote: > Hallo, Alby, > > > My NTP server is running with a Sure GPS as my Stratum-0 device and I'm > > able to get microsecond level of accuracy. Averaging an offset of +/- > 10µs. > > I understand any GPS device needs to know the time down to a precision of > some > 20..50 nanoseconds or so. It simply takes that kind of precision clock > internally to display the position as accurate as these gadgets do. > > Now, some GPS devices may take more care to export the time with good > precision > to the outside than others. Personally, I never had a GPS hooked up as a > clock > source. My ntpd are always stratum 2 or more. But I am surprised that you > get > only +/- 10µs. This is some 200x worse than I would have speculated. > > Are you sure your clock isn't actually much, much better than that? How do > know > it isn't? > > Just comparing with other ntpd out in netland doesn't count. Ntpd will > allow you > to see clock imprecision up to somewhere in the single-digit µs range, if > you > are careful and a bit lucky. Below that, with today's typical network > package > delays, ntp is blind. So you'd need something else, something better than > plain > ntp, to compare your clock to. > > Mildly related to your original question: I find > http://www.leapsecond.com/ > amusing and enlightening reading. Among other things, > http://www.leapsecond.com/ten/ has a list of increasingly precise clocks > and > what they can achieve. > > Regards, Andreas > > > > Am 13.08.2012 20:52, schrieb AlbyVA: > > > > > > > > My NTP server is running with a Sure GPS as my Stratum-0 device and I'm > > able to get microsecond level of accuracy. Averaging an offset of +/- > 10µs. > > > > So I'm wondering, what device out there (that is "reasonably priced") > will > > provide nanosecond level accuracy? > > > > -Alby > > > > > > _______________________________________________ > > pool mailing list > > [email protected] > > http://lists.ntp.org/listinfo/pool > > _______________________________________________ > pool mailing list > [email protected] > http://lists.ntp.org/listinfo/pool
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