Re: Leap second reminder - Check your NTP

[Jared Mauch <jared () puck nether net>]

On Sat, Dec 31, 2005 at 05:06:59PM -0800, Roy wrote:
> 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

        Are they a GPS sync (or do you know?)

        The GPS system doesn't really handle the leap
second situation the same as others, there is a little blurb
here that talks about it:

http://gpsinformation.net/main/gpstime.htm

        I know that I saw my GPS output the following:

@051231235958
@051231235959
@060101000000
@060101000000
@060101000001
@060101000002
@060101000003

        Which is mostly correct, it should have really read 5960 instead.

        I saw my el-cheapo clocks drift by a second at midnight utc.

        I suggest changing your clock sources to something more reliable
if you're seeing folks that are not diligent stratum-1 sources.

        I suggest this as a source:

        http://www.stupi.se/Time/

        I'm kinda curious what CDMA network clocks said around this time
or if they just drifted, i'm sure someone here put their cmda phone in debug
and watched it.

        - jared

-- 
Jared Mauch  | pgp key available via finger from jared () puck nether net
clue++;      | http://puck.nether.net/~jared/  My statements are only mine.