✘sys_fuzz * ntp_random()

[Gary E. Miller]

Yo Eric!

On Tue, 24 Jan 2017 16:42:42 -0500
"Eric S. Raymond" <esr at thyrsus.com> wrote:

> Achim Gratz <Stromeko at nexgo.de>:
> > You might have enough other noise in any particular system so the
> > sys_fuzz (which whitens the quantization noise on the clock reading)
> > doesn't make a difference or you might not.  But presumably Dave
> > Mills didn't put it in there just because he was trying to add
> > useless code.  
> 
> That's what bothers me, that I don't know what we was thinking.

Grr, you motivated me to actually research this.
 
Dr. Mills was in the discussion, but it is not exactly primordial.
sys_fuzz was added in 2011:

    commit b24b87c768265963557e1abb9a859490f929c057
    Author: Dave Hart <davehart at gmail.com>
    Date:   Sat Dec 17 02:30:42 2011 -0500

	[Bug 2037] Fuzzed non-interpolated clock may decrease.


Bug 2037:

    http://bugs.ntp.org/show_bug.cgi?id=2037

It seems most of the bug is about making the clock monotonic and
increasing, not about anything else.

The main point of the fuzz seems to be:

"This strategy preserves the nonce value of the low-order bits of
timestamps on the wire,"

To my mind, as long as the random fuzzing is below sys_fuzz, and it
is, then for my purposes it is too small to worry about.  OTOH, if
it gets in the way of something in the future I'd toss it out.  Just
preserving the nonce aspect.

> Mark, is it time to try to open contact with Mills yet?

I'm not sure this is the issue, but why wait?  He should know about
the current lives of his spawn.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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