[ntp:questions] Re: no more leap seconds?

mike michael.no.spam.cook at wanadoo.fr
Tue Aug 9 20:39:15 UTC 2005


David L. Mills wrote:
> Adrian,
> 
> Thanks for that. There have been 22 leap seconds over the last 33 years 
> and we haven't crashed an airplane yet. Now, let's hear about the real 
> reason.
> 
> I have noticed a couple of things. The broadcast networks used to start 
> programs one second late after hands-up in order to allow some slack for 
> the affiliates, but it seems they no longer do that. So, everybody 
> should be glued to the tube on the occasion of leap and see if the start 
> of the midnight program is one second early.
> 
> I don't remember whether PBS or NPR ever did that, but I do know NPR 
> uses NTP. Think about that; it's not trivial with a real-time broacast 
> of compressed video over a satellite when NTP synchronizes over the 
> satellite. Comes now the huff-'n-puff. Works great and I have some data 
> to prove it.
> 
> Dave
> 
> Adrian 'Dagurashibanipal' von Bidder wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
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>> Clinging to sanity, moi mumbled in his beard:
>>
>>
>>>>    [...]
>>>>    "Safety of life is an issue," said William Klepczynski, a senior
>>>>    analyst at the State Department in favor of the U.S. proposal,
>>
>>
>> who
>>
>>>>    asserts that programmers who ignore the need to add leap seconds
>>>>    present a "risk to air travel in the future" because a glitch
>>>>    might shut down traffic-control systems.
>>>
>>>
>>> Bogus. critical systems should not even need precise time, but be
>>
>>
>> based
>>
>>> on the ordering of events in time. Given the propagation delay on
>>> wide-area (or even networked) systems, even a "radio silence" of one
>>> second should do no harm.
>>> Local transaction-oriented distributed systems should have this
>>
>>
>> solved,
>>
>>> by now, anyway.
>>
>>
>>
>> Ordering of events is very, very difficult to do properly in a world
>> wide, very much decentralised system.  Tagging all events with a
>> timestamp is a realistic solution to this problem - and obviously needs
>> a proper definition of the time base used.
>>
>> If omitting leap seconds (which are, right now, reasonably well-defined
>> AFAICT) would actually simplify this kind of system enough to justify
>> it is imho questionable.
>>
>> - -- vbi
>>
>> - -- Klein bottle for rent -- inquire within.
>>
>> -----BEGIN PGP SIGNATURE-----
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>>
>> iEYEARECAAYFAkL481MACgkQi6Qxi+Wn99ZRRgCdEQtwNIhoPKFdd527vy7ZNS0J
>> dX4AnjKIrprlbTwi+nwhTJGcTH+f7N7g
>> =3fsc
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Real reason?
  When the American governement (any other for that matter) starts doing 
something in secret, it indicates that there is something more inciduous
behind it. Anyone's guess, but as any states preocupation with safety 
can be boiled down to the number of votes up for grabs, I very much 
doubt that there is the remotest link. As Dave says, there has not been 
any recorded safety issue related to leap seconds.
I doubt that NBC et al have any interest there either.

There must be some national security (viewed from the States side) issue
involved. Maybe their programmers do not know how to handle LSs or 
forgot about it in some earlier programme.

My guess is some weapons guidance, or cryptographic problem.




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