Re: [Ntp] Leap second draft

[Warner Losh <[e-mail]>]

On Mon, Apr 1, 2019, 5:54 AM Tony Finch <[e-mail]> wrote:

> Warner Losh <[e-mail]> wrote:
> >
> > And it's less obscure than the crazy notion that leap seconds could
> happen
> > any time other than June and December as a practical matter.
>
> RFC 5905 allows for monthly leap seconds. There's a chance we will need
> more than two leap seconds in a year before the end of this century.
>
> Some of the problems with leap second signalling are because NTP clients
> only get a two bit warning signal, which isn't enough especially if the
> server is setting the bits using assumptions about how leap seconds are
> currently administered (at most every 6 months), and the client is
> interpreting it according to RFC 5905 and TF.460 (at most every month) and
> the server incorrectly provides more than one month warning.
>
> I think if the server explicitly tells the client when the leap second(s)
> occur, then there's less scope for problems caused by unwarranted
> chumminess with the IERS's bulletin C schedule.
>

That would help. GPS give such a signal and it's quite helpful to know past
and future leaps to act as a sanity check on the data. Though in GPS' case,
it is needed because of the 1024 week wrapping issue.

We no longer live in an era where an extra 32bit word would kill us, yet
that would be extremely helpful if widely implemented.

Warner

Tony.
> --
> f.anthony.n.finch  <[e-mail]>  http://dotat.at/
> Lyme Regis to Lands End including the Isles of Scilly: East becoming
> variable,
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> Moderate or good.
>