[ntp:questions] When can I get leap second indicator by ntpd

Jochen Bern Jochen.Bern at LINworks.de
Fri Mar 7 11:37:40 UTC 2014

On Fri, 7 Mar 2014 14:02, Michael Tatarinov wrote:
> 2014-03-07 13:52 GMT+04:00, Harlan Stenn <stenn at ntp.org>:
>> > Williams Catherine writes:
>>> >> I want to know when I can get the leap second indicator by tool ntpq.
>> > Up to a month in advance.
> but not ntp4.2.7, it's up to a day.

NTP peerings merely *forward* the indication (except for some rare
exceptions, i.e., ntpd with installed leapseconds file), so you'll get
it whenever your current sync path's ultimate source (clock) gets aware
of the upcoming leap second, plus propagation delay.

IIRC DCF77 starts broadcasting a leap announcement about one hour prior
(historic observation, not an official spec), some other distribution
systems (that I don't remember by name offhand) do not provide such an
indicator at all, etc..

Note, too, that ntpd (at least the somewhat elder-lish versions I've
seen) does contact its peers more often as one of the four yearly leap
second slots approaches, so as to speed dissemination of leap indication.

								J. Bern
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