Newsflash: Leap Second Update
Update due to leap second
This newsflash provides information regarding the leap seconds themselves, along with an explanation on the impact of the following systems;
- Juniper Networks
- F5 networks
- Arbor Networks
Which systems are in General affected and which not?
Most modern ict equipment is updated by the NTP protocol or the PTP protocol. Systems that do not run these protocols will not be affected by the drift change of the clock, cause they run their local clock. At a specific time, the worldwide NTP atomic servers, will adjust the clock 1 second. This results in a double second or a one second modification to 61 seconds. This can very per clock server. This change can have a momentary affect on systems which can in turn result in a instable or crashing system at the specific drift moment.
Time of Impact
At 30 June 2015, 23:59:60 all NTP servers will receive an corrected clock adjustment.
When to take action due to the leap second
Systems like routers, switches, servers etc. that are updated by an NTP or PTP client should be evaluated by the contents of this document and precaustion could be necessary. For Systems that do not run an NTP client or PTP client, there’s no risk and no action should be taken.
NTP automatic time synchronization works only if the time on the two systems are very close. Very close means between 128 milliseconds and 128 seconds apart. Above this, the time is not changed at all. If that’s the case, you should sync your systems manually.
If systems are NOT configured to use NTP or PTP, no steps need to be taken, cause apparently there’s no automatic update of the system time.
Juniper routers and switches supports 'leap second' adjustment.
If the NTP server is aware of the leap second calculations, then JUNOS router will also add the 1 sec delay by default. Nothing specific needs to be done on the routers to enable this.
If the time is more than 1000 seconds off, NTP records a system log message:
Mar 16 16:41:41 5htp-fxp0 xntpd: time error 4217 over 1000 seconds; set clock manually
If the time is this far off, you need to reset the clock manually:
[email protected]# set date ntp
This command uses the NTP servers that you have configured. You do not have to reboot the router for the new time to take effect.
F5 systems that are configured to synchronize their clocks with an NTP server will automatically process the leap second and adjust their clocks as expected.
For BIG-IP systems that are configured to use an NTP server, the leap second will be processed automatically and logged to the system log. Two consecutive seconds will have the time stamp of midnight UTC immediately following the leap second. In this case, it would mean the timestamp 2015-07-01.00:00:00 UTC would last for two seconds.
Arbor products have been audited for potential issues related to 'leap second' and there are currently no known issues with supported releases of any Arbor product.
A leap second is a one-second adjustment that is applied occasionally to Coordinated Universal Time (UTC) in order to keep its time of day close to the mean solar time.
There should be no negative effects following the insertion of a leap second. If an Arbor system is configured with an NTP server, the device will drift its clock, following the adjustment of the time on the NTP server.
Voor meer informatie kunt u contact opnemen met Infradata op +31 (0)71 750 1525 of per mail naar [email protected].
More Information on the leap second
Leap seconds are a periodic one-second adjustment of Coordinated Universal Time(UTC) in order to keep a system's time of day close to the mean solar time. However, the Earth's rotation speed varies in response to climatic and geological events, and due to this, UTC leap seconds are irregularly spaced and unpredictable.
The basic time for mostly all of the world's local time zones is called Coordinated Universal Time, UTC, which is derived from a bunch of atomic clocks which are distributed in several countries all over the world. The rotation of the earth is not very constant and varies a bit over time, while decreasing the mean rotation speed slowly. This is the reason why so called leap seconds are inserted into the UTC time scale, they adjust process of the UTC time to the real earth rotation.
Why this extra second? It exists because the rotation of the Earth on its axis, which determines the passing of days and nights, slows down over a long period, mainly as a consequence of Moon-Sun attraction effects. In addition, the Earth is affected by its internal (core, mantle) and external (atmosphere, oceans) constituents. Nowadays, though, time is measured largely by 250 atomic clocks belonging to several countries, which function by measuring the transition of energy levels in an atom. Together these clocks are used to calculate UTC, and as this time measuring mechanism is independent of the Earth periodically the two must be brought into alignment with a leap second. In addition, we have to consider that the length of the day is nowadays 2 ms longer than in the year 1820. Not surprisingly then, the Earth's rotation slowly gets out of synchronization with UTC.
The International Earth Rotation Service, IERS, is measuring the true earth rotation and determines when a leap second has to be inserted. Insertion of a leap second is always scheduled for the end of the last day of a month, preferably at the end of June or December, at UTC midnight. In the past all leap seconds had been inserted at either one of those times(*). Announcements whether a leap second is scheduled or not are published by the IERS in their Bulletin C. The current Bulletin C is published about half a year before the next possible date for a leap second.
The IERS Bulletin C #30 from July 2005 announced a leap second to be inserted at the end of December 31, 2005, at UTC midnight. This was the first leap second that had been inserted since the end of 1998. This is why many applications which had been developed during the previous 7 years could not handle the leap second correctly.
Since, the leap second was inserted at the same moment all over the world, the local (civil) time of the insertion depends on the local time offset from UTC, e.g. if the time zone is UTC +3h then the leap second will be inserted when the wall clocks show 3 hours after midnight.