[ntp:questions] Leap Second on NTP server at stratum 2
Jochen Bern
Jochen.Bern at LINworks.de
Wed Jun 10 14:42:53 UTC 2015
On 06/10/2015 01:27 PM, Kashif Mumtaz Tahir wrote:
> Dear Macro,
> We just want to sync seamless with leap seconds. [...]
> Should we need to change/tune anything.
I read your description as:
-- There is a GPS device that actually *speaks NTP* (as opposed to,
e.g., being connected to a server with a serial cable)
-- This device feeds a central stratum 2 server running ntpd
-- Everything else of interest is an NTP (not SNTP) client of
that central server
-- No special configs beyond the above, in particular,
-- no additional external NTP servers,
-- no leap seconds file, and
-- no suppression of stepping
configured on any of the machines.
My conclusions:
-- Whatever announcement the GPS unit makes of the upcoming leap second
will be forwarded to the various machines.
-- You hopefully have historic records, vendor statements, or whatever
indicating that this GPS unit *will* announce a leap second to be
*inserted*.
(It mistakenly announcing a *negative* leap should be highly
improbable, but I have no idea how likely it is to find a GPS unit
that flat out doesn't propagate leap second announcements.)
-- The job of actually "executing" the leap second will be left to the
OS kernel of every individual machine - if you cannot afford them
hitting a historic or new bug that night, you should start testing
kernel versions with simulated leap seconds ASAP.
-- There is a (very small) chance that in the leap second night, your
single-point-of-failure GPS unit will somehow cease to work before
any announcement happens and your platform will never learn of the
upcoming leap second - in which case you'll find it working but
being offset by one second in the morning.
Regards,
J. Bern
--
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