Replacing C

[Kurt Roeckx]

On Sun, Jan 08, 2017 at 04:53:57PM -0800, Gary E. Miller wrote:
> Yo All!
> 
> On Mon, 9 Jan 2017 01:30:30 +0100
> Kurt Roeckx <kurt at roeckx.be> wrote:
> 
> > > That said, I continue to admire your cut right to the heart of the
> > > issue. ntpd spends enough time in I/O waits that I do not think
> > > latency spikes will otherwise induce any problems above measurement
> > > noise.  
> > 
> > The extra packet will improve the precision. It will eliminate
> > one source of jitter.

I should probably have added that it will improve the accuracy
too.

> > And I guess there will be people who would
> > want to use it, but now have to use PTP.
> 
> Now that is an interesting idea.  Could NTP hook into the hardware
> level timestamps that PTP uses?

I thought we were already talking about that ...

> > They probably have the
> > right hardware for it to be really useful.
> 
> Very finicky.  I've tried PTP on a number of different ethernet
> chips.  Most chips do not support hardware PTP all.  Most chips that
> say they support hardware PTP have weird bugs.  Only a few have really
> worked for me.
> 
> Hard to fix too, since the problems are baked into the silicon.

The hardware stamps depend on support of both MAC and the PHY to
begin with, and that you have drivers that support them.

> Some network switches are smart enough to fast tack PTP packets, if
> we can prove they are the bottleneck they could be fixed.

Some switches are PTP aware and do more than just fast track them.

> > But then I have no idea if someone actually tried something like
> > this over the internet with standard hardware and what the effect
> > of it is.
> 
> Then you can be the first.

I have no time for this other than maybe help test it.


Kurt