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Re: [gpsd-dev] Clarifications needed for the time-service HOWTO

From: Gary E. Miller
Subject: Re: [gpsd-dev] Clarifications needed for the time-service HOWTO
Date: Thu, 24 Oct 2013 16:05:20 -0700

Yo Eric!

On Thu, 24 Oct 2013 18:54:09 -0400
"Eric S. Raymond" <address@hidden> wrote:

> Gary E. Miller <address@hidden>:
> > Eic, you have been running for a while, what do you see?
> Haven't taken measurements yet. It was on my to-do list for after the
> content settled down.  Which means soon; maybe tomorrow or this
> weekend.
> My plan is to actually run the whole tuning and measurement procedure
> we describe using the EVK 6H on RS232.  Maybe build some tools 

Actually see if the document is complete?  Oh, the horror.

> > Best way to play this game is not to play.  We can't agree on
> > 'typical' so just don't go there.  Just say that stratum is just a
> > hop count.
> Er...I don't think so.  For practical purposes that's the single most 
> important error bound in the entire document.  If we say nothing
> about it the readers will feel cheated, and I believe justifiably so.

We need to say something about it.  But we need to say it is more
dependent on the users internet connection, and the path to the chimers,
than the chimers themselves.

> The proper thing to do here, I think, is give a range of measurements
> and say "This is what we've observed.  These are other peoples'
> observations. Take with small Siberian salt mine."

Yes.  And that will take a range of answers.o
So far I;ve been seeing under +/- 10 mSec offset and under +/- 1
mSec of jitter, but that is on a high speed connection on the lightly
loaded server.

> Even if we end up with an order-of-magnitude range and a note saying
> "For such an important number this one is controversial and hard to
> pin down" that will be better than punting the issue.

Yes.  I don't mean to punt it, but rather mention it is an attribute
the user has, not the chimer.

Be sure g et a cable modem user, those are aweful.

> And now you know why I want to install Macx-1s on a bunch of routers 
> and profile the hell out of NTP.

Yeah.  And now the PPS JSON number is real it might mean something.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
        address@hidden  Tel:+1(541)382-8588

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