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[Ntp] Antw: Re: Antw: [EXT] Re: New Version Notification for draft‑gruessing‑ntp‑ntpv5‑requirements‑03.txt

Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de> Tue, 19 October 2021 08:05 UTC

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Date: Tue, 19 Oct 2021 10:05:36 +0200
From: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>
To: imp@bsdimp.com, mayer@pdmconsulting.net
Cc: doug.arnold=40meinberg-usa.com@dmarc.ietf.org, james.ietf@gmail.com, "ntp@ietf.org" <ntp@ietf.org>
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Subject: [Ntp] Antw: Re: Antw: [EXT] Re: New Version Notification for draft‑gruessing‑ntp‑ntpv5‑requirements‑03.txt
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>>> Warner Losh <imp@bsdimp.com> schrieb am 18.10.2021 um 16:54 in Nachricht
<CANCZdfqzduC=9oxhqgNJdxUqveRp=WyO+WNXHJTJZ01EO7jTAA@mail.gmail.com>:
> On Mon, Oct 18, 2021 at 8:10 AM Danny Mayer <mayer@pdmconsulting.net> wrote:
> 
>>
>> On 10/18/21 1:49 AM, Ulrich Windl wrote:
>> >>>> Doug Arnold <doug.arnold=40meinberg-usa.com@dmarc.ietf.org> schrieb
>> am
>> > 15.10.2021 um 17:53 in Nachricht
>> > <
>> 
> DB8PR02MB57726795E3AD479F0CCFA778CFB99@DB8PR02MB5772.eurprd02.prod.outlook.co 
> m
>> >
>> >
>> >> Hello James,
>> >>
>> >> I agree that leap smearing is a clumsy and dangerous way to avoid the
>> >> complication of correctly handling leap seconds in distributed database
>> >> software.  And if it was up to me all IT equipment would use TAI for all
>> >> timing except what is displayed to humans.  But it is not up to me.  The
>> >> people who are making the call tell me that they believe that leap
>> seconds
>> > is
>> >> less bad than either moving everything from UTC to TAI, or writing and
>> >> debugging database software that manages leap seconds properly.
>> >>
>> >> So given that state of affairs.  What do we do?
>> > Hi!
>> >
>> > I guess the standard C library needs new functions to get the correct
>> time
>> > first ;-)
>> > time_t has a problem
>>
> 
> Yes. The fundamental problem is that POSIX says there's no such thing
> as leap seconds in time_t. They don't exist, they don't have a unique
> encoding. And any way you represent them (there's at least 3 I know
> of) is ambiguous. This is the reason why smearing is a thing.
> 
> 
>> > Amazingly gettimeofday can use struct timezone, while clock_gettime()
>> can't.
>> > So adding the TAI offset to struct timezone would not help much.
>>
> 
> Look at the 'right' timezones.
> 
> But clock_gettime passes in the 'clock' that you want. You can ask for
> TAI time, but you still have the ambiguity.

In my version of Linux (rather "new" regarding "industry standards") such a flag does not exist.

...

Regards,
Ulrich

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