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Re: [gpsd-dev] Updated docs on NTP segment management

From: Miroslav Lichvar
Subject: Re: [gpsd-dev] Updated docs on NTP segment management
Date: Thu, 26 Feb 2015 11:44:22 +0100
User-agent: Mutt/1.5.23 (2014-03-12)

On Wed, Feb 25, 2015 at 11:03:15AM -0800, Hal Murray wrote:
> address@hidden said:
> > Yeah, I've already found some fields that I'd like to add to the protocol,
> > but didn't do it to not break the compatibility. 
> What did you have in mind?  I'd like to make sure we collect all the good 
> ideas while this discussion is going on.

Precision (this is in SHM but not chrony SOCK), dispersion, delay,
root dispersion, root delay, stratum. This could be used for NTP
sources as refclocks.

Also, it would be good to have some special value for unknown to not
force the clients to put there some random value which would just make
things worse.

> Would it have made sense to use the dummy slots in the current SHM?  (assume 
> we could find a way to avoid collisions)

I think it would but how would it signal that the fields are set to
not use some random garbage the client had on stack? Include a

With the nanoseconds extension that was easy as we can compare the
values to the microseconds fields. If it nanoseconds / 1000 ==
microseconds, we know the client has either set these fields correctly
or it matched by pure chance and the error is smaller than microsecond
and so it's not a problem.

Miroslav Lichvar

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