[ntp:hackers] Re: NTP and leap-seconds

David L. Mills mills at udel.edu
Sun Jul 2 13:57:24 UTC 2006


The usual behavior is that servers do not realize a leapsecond is 
pending, either because they have not been told using ntpdc or the 
radios or drivers do not implement the warning. So the code sifts from 
among the (usually) three survivors of the mitigation algorithms and 
sets the leap if one or more show leap. You suggestion would change that 
to require two out of the three to set the leap. What if there are only 
two survivors?

The most reliable and secure solution to the false alarm problem is to 
run Autokey and use the leapsecond table as distributed from the primary 


David J Taylor wrote:

> Folks,
> I recently had a glitch at 00:00 UTC on 2006 July 01 which I have 
> traced to a server telling me a leap-second was due when it was not.
>  http://www.david-taylor.myby.co.uk/ntp/ntp-events.htm#2006-07-01
> Whilst I haven't been able to check which server gave this indication, 
> it may have been one of the UK pool servers. The glitch I had leads to 
> a couple of questions:
> - is there some sort of sanity check in NTP about leap-seconds, such 
> as requiring a majority of servers to say that a leap second is due 
> before a client actually inserts the leap second?
> - wouldn't it be helpful if NTP logged which server had told it to 
> make the leap-second adjustment?  At the moment, all that gets 
> recorded (at least in the Windows event log) is that fact that the 
> client was told to insert the leap second and when, but not by whom.
> Thanks,
> David

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