My first positive structural change to NTP

Eric S. Raymond esr at
Sun Jun 26 12:41:05 UTC 2016

Achim Gratz <Stromeko at>:
> Eric S. Raymond writes:
> > Here's how I think it should look:
> >
> > ----------------------------------------------------------------------
> > refclock shm unit 0 refid GPS
> > refclock shm unit 1 prefer refid PPS
> > ----------------------------------------------------------------------
> I think that's still perpetuating a mistake.  This whole business of
> having to specify two servers (or refclocks) for the same thing should
> go away.  In fact, some of the PARSE drivers already get it right and
> use (default) device names for this association if you use their PPS
> enabled modes.  This could be done across the board, so that the prefer
> keyword isn't needed anymore just to associate the PPS source with a
> refclock.  It's easy enough these days to tell udev what each device
> should be named, so in principle there wouldn't even be a need to use
> anything but the default names.

I think I disagree.  But I haven't put a lot of thought into this yet
and don't have a strongly-held position; you might persuade me.

The reason I disagree is I think you're overfocusing on the fact that
both refclocks are the same physical device and underfocusing on the
fact that they're two different data channels, possibly with different
fudges and modes.

*Because* fudges and modes may differ, I think it is right for the
configuration syntax to be data-channel-focused rather than
device-focused.  Doing it the other way could land you in a spot
where you want to specify differing per-channel behavior but cannot.

The prefer keyword may be a separate issue, and dispensable.  But
I think that is a different, more specific argument.
		<a href="">Eric S. Raymond</a>

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