nanog mailing list archives
Re: NTP question
From: Harlan Stenn <stenn () nwtime org>
Date: Wed, 1 May 2019 19:30:16 -0700
Hi Keith, On 5/1/19 6:17 PM, Keith Medcalf wrote:
If your network is air gapped from the Internet then sure. If it's not, you can run NTP against a reasonably reliable set of time sources (not random picks from Pool) and be able to say, "my log timestamps are accurate to +/- 10 milliseconds so it must be you who is farked up." While my milliseconds loses the pecking order contest, it's just as good for practical purposes and a whole lot less expensive.You mean something like this, which is relatively easy to achieve: ============================================================================== offset -0.000009, frequency -0.823, time_const 30, watchdog 238 synchronised to NTP server (192.5.41.40) at stratum 2 time correct to within 12 ms polling server every 1024 s ============================================================================== remote refid st t when poll reach delay offset jitter ============================================================================== +clock.sjc.he.ne .CDMA. 1 u 287 1024 377 64.313 0.337 0.867 -tock.usnogps.na .IRIG. 1 u 5 1024 377 103.080 -2.097 0.316 -tick.usnogps.na .IRIG. 1 u 806 1024 377 103.053 -2.328 0.363 +india.colorado. .NIST. 1 u 270 1024 377 41.214 -0.159 0.113 +time-b-b.nist.g .NIST. 1 u 984 1024 377 42.609 0.200 0.045 +time-c-b.nist.g .NIST. 1 u 180 1024 377 42.563 0.201 0.064 +time-a-b.nist.g .NIST. 1 u 163 1024 377 42.639 0.137 0.032 *192.5.41.40 .PTP. 1 u 235 1024 377 12.756 -0.388 12.479 -192.5.41.41 .IRIG. 1 u 312 1024 377 13.575 -1.172 2.425 LOCAL(0) .LOCL. 10 l - 64 0 0.000 0.000 0.000 ------------------------------------------------------------------------------ pll offset: -8.474e-06 s pll frequency: -0.823 ppm maximum error: 0.123149 s estimated error: 0.000122 s status: 2001 pll nano pll time constant: 10 precision: 1e-09 s frequency tolerance: 500 ppm ==============================================================================
That all looks great except for the LOCAL clock at S10. In the event you lose connectivity to the outside, this system will jump from S2 to S10. Depending on the setup of your other systems, groups of them will go sailing off in their own directions. http://support.ntp.org/bin/view/Support/OrphanMode is the better solution. If you cannot do that for some reason, please see the "Dual Time Servers" case at http://support.ntp.org/bin/view/Support/UndisciplinedLocalClock . -- Harlan Stenn <stenn () nwtime org> http://networktimefoundation.org - be a member!
Current thread:
- Re: NTP question, (continued)
- Re: NTP question Mike Hammett (May 01)
- Re: NTP question Brandon Martin (May 01)
- Re: NTP question Harald Koch (May 01)
- Re: NTP question Brandon Martin (May 01)
- Re: NTP question Harlan Stenn (May 01)
- Re: NTP question Harald Koch (May 01)
- RE: NTP question Keith Medcalf (May 01)
- Re: NTP question William Herrin (May 01)
- Re: NTP question Rubens Kuhl (May 01)
- RE: NTP question Keith Medcalf (May 01)
- Re: NTP question Harlan Stenn (May 01)
- Re: NTP question Stephen Satchell (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Harlan Stenn (May 01)
- Re: NTP question William Herrin (May 02)
- Re: NTP question Chris Adams (May 02)
- Re: NTP question James R Cutler (May 02)
- Re: NTP question Harlan Stenn (May 02)
- Re: NTP question James R Cutler (May 02)
- Re: NTP question Harlan Stenn (May 02)
- Re: NTP question Eric S. Raymond (May 06)