[ntp:questions] PPS only configuration

Mischanko, Edward T Edward.Mischanko at arcelormittal.com
Tue Jan 15 21:28:03 UTC 2013


I am using the nmea driver to determine the rough time (seconds).  I want to only use the WAN servers incase the GPS/PPS sources fail.  Having the WAN servers with high offsets in the mix is causing me problems with precision.

Regards,
Ed

> -----Original Message-----
> From: questions-
> bounces+edward.mischanko=arcelormittal.com at lists.ntp.org
> [mailto:questions-
> bounces+edward.mischanko=arcelormittal.com at lists.ntp.org] On
> Behalf Of Brian Utterback
> Sent: Tuesday, January 15, 2013 2:38 PM
> To: Edward T. Mischanko
> Cc: questions at lists.ntp.org
> Subject: Re: [ntp:questions] PPS only configuration
> 
> You can't. The PPS feature can only use offsets up to .5
> seconds. If the
> offset is greater than .5 the PPS will synchronize your system
> to the
> wrong second. In essence the PPS just locks the clock to the
> nearest
> second. So NTP PPS is designed to require another source of time
> and
> then on let the PPS kick in when the offset is below .5 seconds.
> If you
> circumvent that requirement, you run the rather high risk of
> being some
> integer multiple of seconds offset from the real time.
> 
> 
> On 01/15/13 13:48, Edward T. Mischanko wrote:
> > How do I configure NTPD so that only the PPS offset is used to
> figure
> > the clock offset, instead of factoring in the surviving back-
> up
> > servers that have bigger offsets?  I only want the back-up
> servers to
> > come into play when, or if, the PPS fails.
> >
> > #
> > enable pps
> > enable kernel
> > enable ntp
> > tos minclock 4
> > tos minsane 3
> > tinker huffpuff 7200
> > #
> > driftfile "/var/db/ntpd.drift"
> > leapfile "/usr/home/ed/leap-seconds"
> > #
> > enable stats
> > statistics loopstats
> > statsdir "/usr/home/ed"
> > filegen loopstats file loop type day
> > #
> > server 127.127.20.0 mode 18 minpoll 3 prefer
> > fudge 127.127.20.0 time2 0.374000
> > server 127.127.22.0 minpoll 3
> > fudge 127.127.22.0 flag2 0 flag3 1
> > server 192.168.1.254 iburst minpoll 6 maxpoll 6
> > server tick.cerias.purdue.edu iburst minpoll 6 maxpoll 6
> > server tock.cerias.purdue.edu iburst minpoll 6 maxpoll 6
> > server tack.cerias.purdue.edu iburst minpoll 6 maxpoll 6
> > server nist1-chi.ustiming.org iburst minpoll 6 maxpoll 6
> > server nist.expertsmi.com iburst minpoll 6 maxpoll 6
> > server nist.netservicesgroup.com iburst minpoll 6 maxpoll 6
> > server ntp.your.org iburst minpoll 6 maxpoll 6
> > server navobs1.wustl.edu iburst minpoll 6 maxpoll 6
> > server utcnist2.colorado.edu iburst minpoll 6 maxpoll 6
> > server time-a.timefreq.bldrdoc.gov iburst minpoll 6 maxpoll 6
> > server ntp1.conectiv.com iburst minpoll 6 maxpoll 6
> > server east-pool.ustiming.org iburst minpoll 6 maxpoll 6
> > #
> > _______________________________________________
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> > questions at lists.ntp.org
> > http://lists.ntp.org/listinfo/questions
> 
> 
> --
> blu
> 
> Always code as if the guy who ends up maintaining your code will
> be a
> violent psychopath who knows where you live. - Martin Golding
> ----------------------------------------------------------------
> -------|
> Brian Utterback - Solaris RPE, Oracle Corporation.
> Ph:603-262-3916, Em:brian.utterback at oracle.com
> 
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