What's left to doo on NTS.

[Kurt Roeckx]

On Sun, Mar 03, 2019 at 05:59:11PM -0500, Daniel Franke wrote:
> On Sun, Mar 3, 2019 at 8:45 AM Kurt Roeckx via devel <devel at ntpsec.org> wrote:
> > On Sun, Mar 03, 2019 at 05:23:31AM -0800, Hal Murray wrote:
> > >
> > > kurt at roeckx.be said:
> > > > If this is something you're worried about, this can be solved with the
> > > > interleave mode, which was removed.
> > >
> > > How well does it work?
> >
> > It works great, the errors are much smaller when it's enabled.
> 
> Interleaved mode in NTP Classic doesn't do what you think it does.
> 
> The concept behind interleaved mode is sound: get packet timestamps
> from the NIC at the moment they cross the wire, thus eliminating the
> contribution of local buffers to jitter. But ntpd doesn't do anything
> of the kind!
> 
> Actually getting timestamps from the NIC is fairly involved. The NIC
> has its own clock and its own oscillator, which has to carefully be
> kept in sync with the system clock. Furthermore, all the APIs for
> doing this are OS-specific. Check out the linux-ptp project to see
> what it looks like when it's done right; it's a fair bit of code, and
> nothing of the kind is present in ntpd.

But it is present in chrony. It supports both interleaved mode
and hardware timestamping.


Kurt