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Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03 / Message Format

Dan Drown <dan-ntp@drown.org> Fri, 26 November 2021 03:18 UTC

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Date: Thu, 25 Nov 2021 21:18:38 -0600
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From: Dan Drown <dan-ntp@drown.org>
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Subject: Re: [Ntp] comments on draft-mlichvar-ntp-ntpv5-03 / Message Format
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Quoting Miroslav Lichvar <mlichvar@redhat.com>:
> On Wed, Nov 24, 2021 at 10:38:10PM -0600, Dan Drown wrote:
>> For timescale offset, there is an overlap with the unknown value
>> (0x8000/-1.0 seconds) during a negative leap second smear. Is this worth
>> mentioning in the rfc?
>
> Hm, good point. I think it depends on when the leap smear starts.
> There is no +1.0 value. If we define 0x8000 in time16 to mean unknown,
> at least it would be symmetric. +1.0/-1.0 would be rounded to
> 0x7fff/0x8001.

Ok, that rounding makes sense.

Oh, and another thing I've seen people mess up is which sign means  
which clock is faster.  The time formats specify:

* "it is the TAI-UTC offset"
* "it is the UT1-UTC offset"
* "it is the current offset between the leap smeared time and UTC"

Maybe these need to be reworded to be more explicit and follow the  
same phrasing? Something like

* "it is TAI minus UTC"
* "it is UT1 minus UTC"
* "it is the leap smeared time minus UTC"

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