[Ntp] Antw: [EXT] Re: CLOCK_TAI (was NTPv5: big picture)

[Ulrich Windl <[e-mail]>]

>>> Martin Burnicki <martin.burnicki=[e-mail]> schrieb am
07.01.2021 um 16:55 in Nachricht
<[e-mail]>:
> Miroslav Lichvar wrote:
>> On Wed, Jan 06, 2021 at 09:57:56AM +0000, FUSTE Emmanuel wrote:
>>>
>>> I clearly don't understand the resistance to go to a linear TAI like 
>>> form for the core time-stamping format as long as the TAI-UTC offset is 
>>> part of the core protocol frame.
>> 
>> That offset is not always available, e.g. with a DCF77 refclock.
>> Relying on other sources is not always acceptable.
>> 
>>> You will have to do some conversions and adaptations in the OS 
>>> adaptation layer, as today for all NTP implementations, and this layer 
>>> will not be messier as the core is today. No need to wait that operating 
>>> systems fully support a non-leaping timescale, or TAI-UTC offset
natively.
>> 
>> No, it will be messier. That's the other problem.
>> 
>> If your OS doesn't have a TAI clock or it doesn't support timestamping
>> with the TAI clock, you will have to resolve the ambiguity in your NTP
>> implementation. That will not be 100% reliable as you cannot be sure
>> if the timestamp is captured before or after the leap. You are only
>> guessing. If the client doesn't know that the server is only guessing,
>> it may get unexpected errors in measurements and its clock disrupted.
>> 
>> The best thing you can do on such an OS is to suspend the operation
>> around leap second, the same thing as when using a leaping timescale.

Does "around the leap second" mean "until leap smear is complete" in case of
leap smearing?

>> In other words, there is no advantage of using a non-leaping timescale
>> for the time transfer. It would only make things even more messier
>> than they already are.
> 
> Once more, I strongly agree.
> 
> Martin
> -- 
> Martin Burnicki
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