[ntp:questions] Too much offset from GPS?

Richard B. Gilbert rgilbert88 at comcast.net
Fri Mar 7 13:56:50 UTC 2008


chowalit.lab Chowalit Lab Linux wrote:
> Dear all
>    I have problem with my stratum1 box. My box include: freebsd
> 5.2-RELEASE without PPS  , ntp-4.2.0_1, Intel Pentium III, 40 G IDE,
> Germin GPSmap60 , connect with serial com. In GPSmap60 set as NMEA.
> Freebsd box can get NMEA input string. My configuration of ntp.conf
> like this:
> 
> server 127.127.20.0 mode 1 prefer minpoll 4
> server  127.127.1.0 minpoll 5
> 
> server 69.25.96.14 minpoll 6
> server 192.43.244.18  minpoll 6
> server us.pool.ntp.org minpoll 6
> server 203.185.69.60  minpoll 6
> server 122.154.11.67  minpoll 6
> 
> 
> logfile /var/log/ntp
> logconfig =all
> driftfile /var/log/ntp.drift
> 
>    It's look OK. After I start my ntp. And I try to check with "ntpq
> -p", result like this
> 
>     remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> *GPS_NMEA(0)     .GPS.            0 l    -   16    3    0.000   -7.127   7.982
>  LOCAL(0)        73.78.73.84      5 l   22   32    1    0.000    0.000   0.002
>  time.symmetrico .GPS.            1 u   21   64    1  248.084  167.016   0.002
>  time.nist.gov   .ACTS.           1 u   20   64    1  273.165  156.541   0.002
>  andromeda.cs.pu .CDMA.           1 u   19   64    1  295.742  157.582   0.002
>  203.185.69.60   .PPS.            1 u   18   64    1  270.912  292.165   0.002
>  122.154.11.67   .INIT.          16 u    -   64    0    0.000    0.000 4000.00
> 
> 
>   My GPS have offset lower than other stratum 1 server ?? .......
> Please help me.
> 
> 
> Thanks you
> Chowalit

The delay values shown above suggest that you have chosen servers 
located many thousand miles away from your location!  Since the 
potential error in transmitting time from server to client is one half 
of the round trip delay these would appear to be the worst possible 
choices unless they are the only available servers!




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