Leap second reminder - Check your NTP

Sun Jan 1 01:06:59 UTC 2006

Kevin Day wrote:

>
> Last NTP spam:
>
>
> I'm by no means an NTP expert, if anyone else is, please pipe up.
>
> About 30 minutes before the leap second should have occurred, several  
> of our systems reported "xntpd[13742]: time reset 0.958385 s", which  
> was really strange. They moved the wrong direction, and they did it  
> early. Shortly after, those systems lost ntp association and began  
> drifting. About 10 minutes after midnight all have regained sync. I  
> wasn't checking things that early to see why, it's possible some of  
> our NTP sources started disagreeing on what the correct time was, and  
> would also match what other people have reported off-list, going back  
> as far as 18 hours before midnight.
>
> Several public NTP sources are now indicating a "leap second  alarm" 
> (setting the leap bits to 11), which will cause most NTP  clients to 
> rule them out as a source. ntp-2.gw.uiuc.edu is an example:
>
> 130.126.24.44: Server dropped: Leap not in sync
> server 130.126.24.44, port 123
> stratum 2, precision -19, leap 11, trust 000
> refid [128.174.38.133], delay 0.03357, dispersion 0.00049
>
> According to ntpdate, its clock seems to have stopped about 5 minutes  
> before midnight, and hasn't yet recovered.
>
> Other NTP servers haven't cleared their "today is a leap second day"  
> bit, which they should have by now. Some NTP implementations rule out  
> servers that don't agree with what their "master" server thinks the  
> leap second bits should be. My reading of the NTP spec says that at  
> 00:00:00 the leap bits should have been returned to zero. Attempting  
> to sync from one of these servers will produce a "Next leap second  
> occurs at 00:00:00.000 UTC Sun Jan 01 2006" message, but that should  
> be harmless as long as they correct themselves a while before midnight.
>
> Still others have their clocks off by a significant amount(10+  
> minutes) and think they're still in sync, but since I started typing  
> this email, they all have corrected themselves.
>
>
> While I can't say anything broke on our network as a result of the  
> leap second, a good percentage of our gear lost NTP sync or had some  
> kind of NTP problem around midnight UTC. You may want to check your  
> NTP status at some point, in case something drifted quite a way off  
> and won't step itself back now because the difference is too great.
>
> -- Kevin
>

There is at least one stratum-1 server here on the West coast that my 
NTP says is now off by 1 second.  Several stratum-2 are synced to it and 
are now off also.  So checking servers might be a good idea

Roy Engehausen