Re: [Ntp] Negative leap-second?

When we tested both positive and negative leap seconds at PTP plugfest events, we found implementations that handled the positive leap seconds correctly, but not the negative ones.  The faulty list included implementations that looked only at the leap second flag, and never check whether it was forward or backward.  Forward was assumed.

Doug

From: ntp <ntp-bounces@ietf.org> on behalf of Warner Losh <imp@bsdimp.com>
Date: Tuesday, August 2, 2022 at 10:00 PM
To: Harlan Stenn <stenn@nwtime.org>
Cc: Danny Mayer <mayer@pdmconsulting.net>, NTP WG <ntp@ietf.org>
Subject: Re: [Ntp] Negative leap-second?

On Tue, Aug 2, 2022, 7:55 PM Harlan Stenn <stenn@nwtime.org<mailto:stenn@nwtime.org>> wrote:
I don't think this really matters.

The fastest way to make sure that systems will handle leap seconds is to
decide to implement a forward leap second in, say, January, and then a
backward leap second in, say, March.  Then add one in May and subtract
one in July.  Repeat.  When an actual leap second is really needed, just
skip one of these, as appropriate.

Doing this will give folks plenty of opportunity to make sure that leap
second processing code works, on an ongoing basis.

If folks prefer, do these once every third month instead of every other
month.  The trick is to do them often enough that vendors have a clear
reason to get this working correctly.

Yea, do them all the time, or never. Either are good, though I'd prefer the latter. Also a way to make sure it works...

Warner

On 8/2/2022 4:05 PM, Danny Mayer wrote:
> Apparently the earth's rotation is speeding up:
> https://www.timeanddate.com/news/astronomy/shortest-day-2022
>
> If we have to subtract a leap-second I think we will see failures, since
> this is rarely if ever tested.
>
> Danny
>
> _______________________________________________
> ntp mailing list
> ntp@ietf.org<mailto:ntp@ietf.org>
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>

--
Harlan Stenn <stenn@nwtime.org<mailto:stenn@nwtime.org>>
http://networktimefoundation.org - be a member!

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