Re: [Linuxptp-users] UTC Offset on grandmaster?

[Keller, J. E <jac...@in...>]

On Fri, 2015-09-18 at 11:11 -0500, Scott Silverman wrote:
> Thanks for the prompt response.
> 
> As for the patch sent to the mailing list, I just joined, and the
> sourceforge archives are broken (a sourceforge 403 error is
> returned), so I couldn't look back.
> 

Try gmane instead. The sourceforge achives are really bad.

http://news.gmane.org/gmane.comp.linux.ptp.devel

> 
> The offset option is documented, but maybe that is out of date?
> 
> The documentation (man page) for phc2sys lists the following:
>        -O offset
>               Specify the offset between the slave and master times
> in seconds. Not compatible with
>               the -a option.  See TIME SCALE USAGE below.
> 

Yes, but this is not the UTC offset. This is a separate option for a
different type of correction, and what is actually happening here is
the two clocks end up in "sync" but report differently because it
reports UTC time, not the TAI timescale used by PTP, thus the 1 second
offset.

> And then, in TIME SCALE USAGE: 
> Phc2sys acquires the offset value either by reading it from ptp4l
> when -a or -w is in effect
>        or from command line when -O is supplied.  Failure to maintain
> the correct offset can result
>        in local system clock being off some seconds to domain master
> system  clock  when  in  slave
>        mode, or incorect PTP time announced to the network in case
> the host is the domain master.
> 
> Should all of my slaves be picking up the UTC offset from the
> grandmaster? Because none of my slaves report an offset of 35, they
> all report offsets of 36 (in fact, the only other device reporting a
> 35 offset is the first boundary clock hop from the grandmaster, a
> Cisco switch). I'm not clear on how my other slaves (and other
> boundary clocks) are getting their (correct) offsets of 36.
> 

Yes, they should pick up the UTC from the grandmaster. I bet your
boundary clock is separating two networks which one has 35, and the
other has 36...

Regards,
Jake