[ntp:questions] GPS driver failure mode question

Charles Brown charles.brown at sensis.com
Thu Jan 8 22:56:18 UTC 2009


   This seems like it should be a common question, but I can't find it 
on  the Big I.

   I have a processor with a serial GPS on a closed private network.  If 
the GPS is not locked, or the GPS inputs are missing, I still want the 
ntpd to serve *some* time, perhaps from the undisciplined local clock. 
I.e., the server can't just do nothing.  Does the GPS driver do that 
automatically, or do I have to configure two drivers in the ntpd.conf? 
Perhaps something like;

         prefer peer 127.127.20.u
         peer 127.127.1.u

    Suppose I have a second server, with a higher precision oscillator, 
on this same network. How would I configure that?  Perhaps;

         prefer peer morePreciseServer   # should be best source
         peer 127.127.20.u               # next is the GPS
         peer 127.127.1.u                # if all else fails....

    What would the configuration on the other processor look like? Perhaps;

         prefer peer 127.127.22.u  # always best
         peer 127.127.1.u          # if GPS fails, still better for a
                                   #   couple of days
         peer lessPreciseServer    # GPS missing a long time,
                                   #   lessPreciseServer might have GPS

    Should I coerce stratum values?

--CB



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