[ntp:questions] Number of Stratum 1 & Stratum 2 Peers

Martin Burnicki martin.burnicki at meinberg.de
Wed Dec 17 11:07:02 UTC 2014

Rob wrote:
> Martin Burnicki <martin.burnicki at meinberg.de> wrote:
>>> Unfortunately, the same mechanism isn't used for leap seconds.
>>> There would be no problem at all when the system time ticked in TAI
>>> and the addition of the leap seconds is done via some rule table similar
>>> to the local time rules.  ntpd would not even be involved in the problem.
>> Also agreed. However, actually ntpd expects UTC, not TAI.
> Of course it is a hypothetical situation.  When the Unix developers
> would have had the foresight to define their clock in TAI rather than
> UTC, the NTP designer probably would have used TAI as well, and instead
> of the leap second handling there maybe would have been some field to
> broadcast the current UTC-TAI offset.


> GPS actually does it that way.

Yes, I know. I've by myself written a set of routines which decodes and 
evaluates the data broadcasted by the GPS satellites.

IMO the GPS system designers have made quite a number of wise decisions, 
e.g. letting the GPS time simply increase monotonically, which is, from 
a technical/usage point of view, similar to TAI.

AFAIK the GLONASS satellites use UTC instead, which causes an 
interruption in the sequence of data frames whenever a leap second occurs.


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