[ntp:questions] Atomized NMEA using second numbering from other server

Dave Hart hart at ntp.org
Fri Oct 14 16:53:37 UTC 2011


2011/10/14 Miguel Gonçalves <mail at miguelgoncalves.com>:
> Hi all!
>
> This is the billboard from one of my servers (ntp 4.2.6p3):
>
> tock# ntpq -p
>     remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> oGPS_NMEA(0)     .GPS.            0 l    6   16  377    0.000   -0.001   0.003
> +ntp-p1.obspm.fr .TS-3.           1 u    6   64  377   44.396    0.860   1.342
> +ptbtime1.ptb.de .PTB.            1 u   34   64  377   68.039    2.179   0.698
> -ntp1.oma.be     .PPS.            1 u   43   64  377   52.612    4.312   0.819
> *canon.inria.fr  .GPSi.           1 u   60   64  377   44.358    1.177   0.902
> -ntp1.nl.uu.net  .PPS.            1 u   49   64  377   57.991    3.550   0.989
>
> Does the tally code * mean that NTP is getting the seconds from
> canon.inria.fr? The NMEA driver is configured as prefer.
>
> On another server (4.2.7p222) I am getting
>
> tock# ntpq -p tick
>     remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> *GPS_NMEA(0)     .GPS.            0 l   13   16  377    0.000    0.561   1.374
> oPPS(0)          .PPS.            0 l   12   16  377    0.000   -0.001   0.004
> +ntp-p1.obspm.fr .TS-3.           1 u   30   64  377   44.128    1.085   0.779
> +ptbtime1.ptb.de .PTB.            1 u   18   64  377   65.281    0.412  11.300
> -ntp1.oma.be     .PPS.            1 u   26   64  377   52.953    4.699   3.274
> +canon.inria.fr  .GPSi.           1 u   26   64  377   44.764    1.471   1.906
> -ntp1.nl.uu.net  .PPS.            1 u   27   64  377   56.525    2.892   0.987
>
> Here ntp is getting the seconds from GPS_NMEA.
>
> What happens when the first server looses it's connection to the Internet?

The first one is configured with NMEA with PPS enabled.  The second
one is configured with NMEA with PPS disabled, and also with the
PPS/atom driver.  I have a system configured similarly to your first,
with the only refclock source NMEA with PPS enabled, running
4.2.7p214.  It shows the 'o' pps peer tally code for NMEA, and has no
association with the * sys peer tally code -- the LAN sources are all
marked with + or space tally codes.  Are you using "prefer" in the
ntp.conf for the first one?

I would not expect NMEA + PPS of being capable of using anything but
NMEA to number the seconds.  As a result, though, I'd never think to
use prefer in that configuration, so I don't have experience with NMEA
+ PPS while prefer is set on another association.

Cheers,
Dave Hart


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