[ntp:questions] How do I validate my PPS clocks?

bodosom at gmail.com bodosom at gmail.com
Sun Feb 24 23:11:57 UTC 2013


I can't find or figure out how to validate my ntp results.

I (currently) have two Linux boxes with PPS via the NMEA driver from
Garmins (18 & 18x) and a Sure board connected to a purpose built
NTP server.  When I set up my first Garmin all of my remote offsets
were negative which seemed unlikely so I set time1 to 5.3ms which
also seems unlikely but  which brought me into congruence with some
nearby stratum 1 servers.

Below is the output* from an intermediate machine on my home network
(3Mb ADSL) which is temporarily connected to several servers.

192.168.0.2 is running with time1 5.3ms.
192.168.0.244 is running with time1 132us.
192.168.0.210 is the appliance and has currently has no adjustments.**

Should I expect /all/ (ignoring the high jitter ones) of the remote
clocks to have negative offsets?

Is there a sensible to way to make this assessment purely within the
NTP system?

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+192.168.0.2     .GPS.            1 u   14   16  377    0.109   -5.429   0.006
*192.168.0.244   .GPS.            1 u    1   16  377    0.112    0.000   0.008
+192.168.0.210   .GPS.            1 u   15   16  377    0.567   -0.001   0.007
-216.66.0.142    130.207.244.240  2 u   54   64  377   63.526   -7.131   0.192
-38.229.71.1     204.123.2.72     2 u   25   64  377   67.175   -4.368   0.472
-63.240.161.99   72.26.198.233    3 u   19   64  377   70.797   -3.284   0.320
#204.235.61.9    128.105.201.11   2 u   17   64  177   73.331   -9.732   0.426
-216.229.4.69    216.229.0.179    2 u    -   64  377   78.848   -4.987   1.337
-199.7.177.206   64.147.116.229   2 u   13   64  377   86.072   -7.451   0.235
#2604:180::8138: 164.244.221.197  2 u   56   64  377   91.521  -33.681  25.573
-198.101.234.139 128.138.140.44   2 u   35   64  377   97.360   -2.065   0.584
#2604:2880::870: 139.78.135.14    2 u   23   64  377  115.057  -12.785  22.738
-207.7.148.214   204.123.2.5      2 u    2   64  377  123.982   -8.091   0.747


*This billboard is sorted by delay.
**You'd have to recompile the control software.



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