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

[Doug Arnold <[e-mail]>]

I think that the point of a leap smear is that no special handling of leap seconds is needed by the client.  It is introduced gradually over a number of polling periods.

Doug

On 1/8/21, 2:32 AM, "ntp on behalf of Ulrich Windl" <[e-mail] on behalf of [e-mail]> wrote:

    >>> 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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