Replacing C

[Kurt Roeckx]

On Sun, Jan 08, 2017 at 06:02:36PM -0500, Eric S. Raymond wrote:
> Hal Murray <hmurray at megapathdsl.net>:
> > We don't care about the timing in most of the code.  The only critical 
> > section is the chunk between grabbing the time and sending the packet.  That 
> > chunk is likely to involve crypto.
> > 
> > We could fix that with another packet.  The idea is that you get a time stamp 
> > from the kernel on the transmit side.  Then you have to send another packet 
> > to get that time stamp to the other end.
> > 
> > Maybe we should add that to the NTPv5 list.
> 
> No, I'd much rather put in a GC lockout on the critical region than
> complicate the protocol.
> 
> 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. And I guess there will be people who would
want to use it, but now have to use PTP. They probably have the
right hardware for it to be really useful.

But I think in the general case, the jitter caused by the network
will be higher than then what this would win.

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.


Kurt