[time-nuts] GPS jumps of -13.7 us?

NeT MonK netmonk at netmonk.org
Fri Jan 29 15:08:12 EST 2016


On Fri, Jan 29, 2016 at 3:29 PM, Chris Caudle <chris at chriscaudle.org> wrote:

> On Fri, January 29, 2016 1:32 am, NeT MonK wrote:
> > As a side effect of those glitch in the GPS matrix, the utc_valid_flag
> was
> > not anymore set in the stream of the primary master clock, just before my
> > secondary starts to become active (loss of primary stream) which leads to
> > linux server  ptp slave to readjust of +36 seconds and jump backward -36
> > seconds as far as the flags was coming back.
>
> The difference between UTC and TAI is 36 seconds.
>
> Are you running ptpd or linuxptp on your Linux servers?
> It sounds like the ptp agent running on your servers interpreted the lack
> of UTC valid flag to mean that the timestamps were now in TAI, so the
> server kernel applied the TAI to UTC offset to the time received via PTP.


Dear Chris,

I run sfptpd  which is a fork of linux ptpd daemon adapted to solarflare
network adapter.
I will have to fine tune it in order to be more resilient in such scenario.

But i guess it's not very often the gps system as such incident.

Regards



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