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Re: [Ntp] Consensus call: NTPv5 and leap second smearing

Daniel Franke <dfoxfranke@gmail.com> Sun, 02 July 2023 19:22 UTC

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From: Daniel Franke <dfoxfranke@gmail.com>
Date: Sun, 02 Jul 2023 15:21:54 -0400
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To: Dieter Sibold <dsibold.ietf@gmail.com>
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Subject: Re: [Ntp] Consensus call: NTPv5 and leap second smearing
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There are two things I care about:

1. The timestamp on the wire must be something that can be
unambiguously converted to UTC.
2. The packet must contain sufficient information for the client to be
able to apply a noon-to-noon smear if desired.

The NTPv4 behavior of repeating during a leap second insertion is
unacceptable, because this creates ambiguity. Any of the following
would be equally acceptable to me:

1. Timestamps are UTC, represented using two fields: a day number, and
time since midnight. Leap indicator bits MUST be set during precisely
noon to noon .
2. Timestamps MUST be smeared linearly noon-to-noon in proximity to a
leap event. The leap indicator MUST be set when and only when smearing
is in progress.
3. Timestamps are TAI, and information elsewhere in the packet provides:
    a. The TAI time at which the last-announced leap event begins (may
be past, present, or future)
    b. The direction of the event (insertion or deletion)
    c. The TAI-UTC offset at the completion of this event

1 and 2 are perfectly equivalent in what information they provide. 3
is more informative, and therefore nicer for the client but harder for
the server, because it has to have the extra information available.

On Wed, Jun 28, 2023 at 3:56 PM Dieter Sibold <dsibold.ietf@gmail.com> wrote:
>
> Dear all,
>
> at IETF 116 we decided to have two consensus calls regarding the content of the NTPv5 requirement draft. These are consensus calls that we would like to conduct to help progress the NTPv5 requirements document (https://datatracker.ietf.org/doc/draft-ietf-ntp-ntpv5-requirements/). Both consensus calls will run until July 21st 2023 and will be discussed at the next NTP wg meeting at IETF 117 in San Francisco.
>
> The second consensus call:
>
> Regarding leap second smearing:
>
> Currently, the NTPv5 requirement draft states that NTP servers should not apply leap second smearing to transmitted timestamps. Shall NTPv5 support leap second smearing? If yes, shall the NTP server apply leap smearing to the transmitted timestamps or otherwise shall the client perform leap second smearing?
>
>
>
> Greetings
> Karen and Dieter_______________________________________________
> ntp mailing list
> ntp@ietf.org
> https://www.ietf.org/mailman/listinfo/ntp

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