Field Notice: FN - 63981 - Leap Second Adjustment June 30, 2015 Affects Cisco Unified SIP Proxy

NOTICE:

THIS FIELD NOTICE IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTY OF MERCHANTABILITY. YOUR USE OF THE INFORMATION ON THE FIELD NOTICE OR MATERIALS LINKED FROM THE FIELD NOTICE IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS FIELD NOTICE AT ANY TIME.

Revision History

Products Affected

Problem Description

A new leap second will be added to the Coordinated Universal Time (UTC) on June 30, 2015.

There is a possibility that this update might cause a Cisco Unified Session Initiation Protocol (SIP) Proxy (CUSP) module to freeze due to an internal racing condition. If the module freezes, it will be unable to process new calls until it is manually rebooted.

Note: Refer to the Products Affected section for details about the affected CUSP versions.

Background

In order to ensure the correct alignment of astronomical and atomic time, the International Earth Rotation & Reference Systems Service has called for an extra second to be added to the UTC at 23:59:59 on June 30, 2015.

This will be the 26^th leap second adjustment since 1972, and it represents an important consideration for computing, networking, and software solutions providers.

These leap second updates are provided by Network Time Protocol (NTP) servers to the NTP clients via the NTP protocol.

The CUSP modules can be configured in order to derive their time from the NTP servers. In this configuration, the CUSP module might receive a leap second update from the NTP server, which might cause it to freeze/hang.

Leap Seconds Explained

Due to occasional irregularities in the rotation of the Earth, it is possible for the astronomical and atomic times to become out of sync. When that difference exceeds 0.9 of a second, the International Earth Rotation & Reference Systems Service calls for a leap second to be added or subtracted to the UTC.

Problem Symptoms

There is a possibility that a CUSP module might not be affected by the leap second update. Whether a CUSP module will be affected depends on the internal software timing issues. Cisco recommends that customers apply the software fix or one of the workaround options that are described in this Field Notice in order to proactively prevent the problem.

Workaround/Solution

This problem is fixed in CUSP Version 8.5(9). Customers are encouraged to download and install this version in order to prevent the problem.

As an alternative solution, apply one of these workaround options:

• Disable NTP on the CUSP modules, which allows the CUSP module to miss the leap second update. The NTP can then be safely re-enabled after the leap second is missed. Note that the module must be rebooted after you disable NTP.
  
  
• Use an Access Control List (ACL) or Firewall in order to block/break the NTP connection. Similar to the first option, the goal is to ensure that the CUSP module misses the leap second update. The benefit of this option over the first is that a reboot is not required.
  
  
• Run the NTP server in slew mode. In this mode, the NTP server does not send a leap second update to the NTP clients. Instead, it gradually adjusts the time in order to accommodate for the new second.
  
  
• Monitor the CUSP modules during the leap second update and reboot them if they freeze. There is a good possibility that the CUSP module might not freeze (dependent upon internal timing issues). Especially in non-24 hour environments, it might be acceptable to closely monitor the modules during the leap second update and reboot them on an as-needed basis.

Note: For additional information, refer to the Cisco Unified Customer Voice Portal Technical References page.

Note: For more information about leap second updates, refer to the Leap Second Overview.

CDETS

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For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods:

• Open a service request on Cisco.com
• By email
• By telephone

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