Re: [Linuxptp-devel] addition of a "get frequency" op?

[Dale S. <ds...@us...>]

On Tue, Jun 10, 2014 at 2:57 PM, Richard Cochran <ric...@gm...>
wrote:

> On Tue, Jun 10, 2014 at 12:11:25PM -0400, Dale Smith wrote:
> > Isn't this basically the observedParentClockPhaseChangeRate in the parent
> > data set? (but with whacky units)
>
> Hm, I thought that was the observed difference *after*
> adjustment. If you are right, then it should be easy to provide this
> value.
>

Good question.  I don't know.


> > I know linuxptp doesn't implement this, along with
> > observedParentOffsetScaledLogVariance.  Should it?
>
> Well, this is an optional calculation that seems to me to be just busy
> work. What is the point of measuring this anyhow?
>

I'm no math wizard, but I believe this is basically a metric of how noisy
the clock is.

The reason it is needed is that the specs say you need to report BOTH the
phase
change rate and the variance. (in section 7.6.4.2 parentDS.parentStats).

My question above (Should it?) is really: is it worth the hassle of
implementing and
calculating the variance to get the more useful (IMHO) phase change rate?


-Dale