North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Leap second reminder - Check your NTP
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 [email protected] clue++; | http://puck.nether.net/~jared/ My statements are only mine.
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