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Re: [Ntp] Comments on Miroslav's NTP v5 proposal.

Kurt Roeckx <kurt@roeckx.be> Mon, 30 November 2020 21:54 UTC

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Date: Mon, 30 Nov 2020 22:54:54 +0100
From: Kurt Roeckx <kurt@roeckx.be>
To: Doug Arnold <doug.arnold@meinberg-usa.com>
Cc: Miroslav Lichvar <mlichvar@redhat.com>, Watson Ladd <watsonbladd@gmail.com>, NTP WG <ntp@ietf.org>
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Subject: Re: [Ntp] Comments on Miroslav's NTP v5 proposal.
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On Mon, Nov 30, 2020 at 09:31:26PM +0000, Doug Arnold wrote:
> One more thing on the correction field.  In my scheme only the client offset is corrected.  The delay is still the real round trip delay, rather than some kind of corrected delay.  I was thinking that the real round trip delay is what matters. Is that right?  

We actually don't care about what the delay is. Delay is a term that
needs to be replaced by something that describers better what we
want to do with it.

Simplified, the delay is used as an upper bound for the maximum
error. We put the offset at half the delay to minimize the maximum
error. Half the delay also happens to be our best estimate for the
time.

If devices between the client and the server indicate that it was
on that device for a certain time, with an indication for an error
on that time, we can reduce the maximum error.


Kurt

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