[ntp:questions] Re: Question to NTP developers

Eugen COCA ecoca at eed.usv.ro
Sat Aug 26 08:50:19 UTC 2006


David L. Mills wrote:
> Eugen,
>
> It's not a good idea to use ntpdc for precision comparisons; ntpq is
> much more useful and truthful.
>
> The display makes no sense. How is it that the GPS and PPS show huge
> jitter while the offsets are zero? Take a look with ntpq at
> rackety.udel.edu and note the offset and jitter.

Dave,

on the best of my servers, ntpq/pe looks like:

     remote           local      st poll reach  delay   offset    disp
=======================================================================
=GPS_NMEA(1)     127.0.0.1        0   64  377 0.00000 -0.000000 0.03049
=ntp3.usv.ro     80.96.120.253    1   64  377 0.00049  0.000053 0.04402
=gps-1.mit.edu   80.96.120.253    1  256  377 0.14613  0.000446 0.12549
=ntp2.usv.ro     80.96.120.253    1   64  377 0.00026 -0.000012 0.06828
=gps-2.mit.edu   80.96.120.253    1  256  377 0.14575  0.000113 0.10460
=ptbtime1.ptb.de 80.96.120.253    1  256  377 0.04861 -0.001742 0.10022
=ptbtime2.ptb.de 80.96.120.253    1  256  377 0.04829  0.000012 0.11932
*PPS(1)          127.0.0.1        0   16  377 0.00000 -0.000000 0.01567
=ntp-p1.obspm.fr 80.96.120.253    1  256  377 0.05722  0.000721 0.09496
=ntps1-1.cs.tu-b 80.96.120.253    1  256  357 0.05438 -0.000242 0.09479


and at the server you indicated is:

     remote           local      st poll reach  delay   offset    disp
=======================================================================
=239.1.1.1       128.4.1.1       16   64    0 0.00000  0.000000 4.00000
=SPECTRACOM(1)   127.0.0.1        0   64  377 0.00000 -0.000007 0.03073
*PPS(0)          127.0.0.1        0   16  377 0.00000 -0.000008 0.01608
=mizbeaver.udel. 128.4.1.1        1   64  377 0.00410 -0.000018 0.05716

I must run the servers with kernel sync disabled in order to see the
differences between the to situation: kernel PPS or driver 22. I wonder
if it make sense to put "flag3 1" - enable kernel pps in the line for
the 22 driver, say "127.127.22.1 flag3 1" ?




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