[ntp:questions] Leap second to be introduced in June

Jochen Bern Jochen.Bern at LINworks.de
Tue Jan 27 14:13:22 UTC 2015


On 01/27/2015 10:16 AM, Terje Mathisen wrote:
> Jochen Bern wrote:
>> Because they chose the long window (about one day) and made it exceed
>> the time an NTP peering needs to *act* on the perceived offset, yes. If
> 
> That's a a key feature of the long adjustment period: The smearing takes
> so long that the frequency offset is never even close to the 500 ppm
> limit, and (since the first derivative is smooth) the change is
> frequency is gradual enough that all the clients will be able to track
> it, even if they are running at a fixed 1024 s polling interval.

OK, but that's assuming that the client will "absorb" the leap second
entirely by having an NTP server dragging it along within the limits of
a normal NTP sync, without *ever* informing the client kernel's leap
second handling routines that one even occurred.

Which means that your client cannot be talking to a normal NTP server
with normal NTP client s/w, and if kernels ever would attempt to keep
track of past leap seconds on their own, *this* client's kernel would
fail in that because it never gets *told* of leap seconds as they happen.

Regards,
								J. Bern
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