[ntp:questions] Offset Average (Normal)?

Alby VA albyva at empire.org
Tue Mar 13 13:24:48 UTC 2012


On Mar 13, 8:27 am, David Lord <sn... at lordynet.org> wrote:
> David J Taylor wrote:
>
> > "Alby VA" <alb... at empire.org> wrote in message
> >news:7824f31d-b72c-44eb-9eeb-b219a7543db3 at gr6g2000vbb.googlegroups.com....
> > []
> >> ntp2.usno.navy. .USNO.           1 u  11h  128    0   21.392
> >> 11.022   0.000
> >> -ntp0.usno.navy. .USNO.           1 u  512  128  370   25.747
> >> -0.242   3.378
> >> +ntp1.usno.navy. .USNO.           1 u   51  128  377   30.361
> >> -1.445   2.473
> >> -time-a.nist.gov .ACTS.           1 u  136  128  336   19.894
> >> 0.582   5.715
> >> +time-b.nist.gov .ACTS.           1 u   64  128   57   19.100
> >> -0.948   2.129
> >> oPPS(0)          .PPS.            0 l   13   16  377    0.000
> >> 0.502   0.153
> >> *GPS_NMEA(0)     .GPSb.           0 l   12   16  377    0.000
> >> -38.705  13.177
>
> > As Chris commented, you should maybe be using a single driver - here's
> > mine for a GPS 18 LVC (which should be similar apart from the baud rate):
>
> > ==============
> > oGPS_NMEA(1)     .PPS.            0 l   16   16  377    0.000    0.004
> > 0.002
> > +feenix          .PPS.            1 u   29   32  377    0.267   -0.027
> > 0.029
> > +stamsund        .PPS.            1 u   13   32  377    0.246   -0.028
> > 0.035
> > -time.hilo.net   130.88.212.143   3 u   67 1024  377   21.717    2.509
> > 1.349
> > -server0.terrybu 140.203.204.77   2 u 1023 1024  377   23.783    3.814
> > 4.331
> > +xinnaeus.bin.ed 129.215.64.32    2 u  677 1024  377   30.284    1.405
> > 0.739
>
> > and the configuration:
>
> > driftfile /var/db/ntp.drift
> > #
> > server  127.127.20.1    mode 0  minpoll 4 maxpoll 4  prefer
> > fudge   127.127.20.1    flag1 1 flag3 1 refid PPS
> > #
> > server 0.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
> > server 1.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
> > server 2.uk.pool.ntp.org iburst minpoll 10 maxpoll 10
> > #
> > leapfile /root/ntp/leap-seconds.3535142400
>
> > (which has "just grown", so may not reflect current best practice).
>
> I've not noticed any significant difference after swapping to
> use only NMEA driver as from March  2, 2012.
>
> Also version of ntpd I was using in 2008/2009 didn't have nmea
> driver with support for PPS.
>
> NetBSD-5
> Garmin 18X-LVC used from 2009 to March 2011.
> Sure GPS used from March 2011 to date.
> Serial cable length was extended by about 17m to confirm that
> working over that distance would not be a problem.
>
> Atom driver used from 2009
> /etc/ntp.conf.11122702
> #############
> server  127.127.20.2  mode 18  prefer
> fudge   127.127.20.2  time2 0.350  refid GPSb
> server  127.127.22.2
> fudge   127.127.22.2  flag2 0  flag3 1  refid GPSb
> #############
>
> peerstats.20120108
>         ident     cnt     mean     rms      max     delay     dist     disp
> ==========================================================================
> 127.127.20.2    1350  -63.925   14.862   50.035    0.000    2.408    1.722
> 127.127.22.2    1350    0.000    0.003    0.030    0.000    0.928    0.928
>
> loopstats.20120108
> loop 1350, 7+/-24.0, rms 3.4, freq -35.89+/-0.159, var 0.078
>
> /etc/ntp.conf.12030801
> #############
> server  127.127.20.2  mode 18
> fudge   127.127.20.2  time2 0.410  flag1 1  flag2 0  flag3 1  refid GPSb
> #############
>
> peerstats.20120312
>         ident     cnt     mean     rms      max     delay     dist     disp
> ==========================================================================
> 127.127.20.2    1350    0.000    0.003    0.028    0.000    0.928    0.928
>
> loopstats.20120312
> loop 1350, 3+/-25.1, rms 3.3, freq -35.13+/-0.204, var 0.054
>
> David



I'll say there has been an improvement, but does this look weird?
What is (oGPS_NMEA) telling me?

NOTES: (Yes I know, I need to increase the minpoll on remote servers.)
------------
     remote           refid      st t when poll reach   delay
offset  jitter
==============================================================================
 utcnist2.colora .ACTS.           1 u   57   64   11   56.500
2.475   2.852
+ntp.alaska.edu  .GPS.            1 u    1   64  357  113.075
-0.537   1.467
-tick.usask.ca   .GPS.            1 u   40   64  377   95.721
-8.491   0.737
+cronos.cenam.mx .GPS.            1 u    5   64  377   88.488
-2.094   1.823
*ntp1.usno.navy. .USNO.           1 u   47   64  377   20.605
2.849   4.014
-time-a.nist.gov .ACTS.           1 u    2   64  203   84.047
38.336  38.109
oGPS_NMEA(0)     .PPS.            0 l    7   16  377    0.000
0.002   0.002




Peerstats Before/After: [day, second, address, status, offset, delay,
dispersion, skew (variance)]
---
Before: 55999 1.493 127.127.20.0 914b -0.015715484 0.000000000
0.002563345 0.023433975
After: 55999 48104.873 127.127.20.0 975a 0.000001154 0.000000000
0.000233462 0.000001907


Offset Before: -0.015715484
Offset After: 0.000001154



This is my current /etc/ntp.conf file (parsed):
--
#
server 127.127.20.0 mode 18 minpoll 4 maxpoll 4  prefer
fudge  127.127.20.0 flag1 1 flag3 1 refid PPS
#







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