February 12, 2007
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.
ACNS - ACNS SW
WAFS - WAFS SW
IPTV - ACNS SW
WAAS - WAAS SW
New U.S. Daylight Savings Times rules go into effect in March 2007. Consequently, customers whose network components rely on the default U.S. summertime clock settings within Cisco Application and Content Networking System (ACNS), Wide Area File Services (WAFS) or Wide Area Application Services (WAAS) software will be affected by the following problem.
For operating systems that have not been updated with the new U.S. DST policy changes, timestamps will exhibit a one hour time clock offset lasting three weeks beginning at 2 A.M. on the second Sunday in March of 2007. They will also exhibit a one hour time clock offset lasting one week beginning at 2 A.M. on the first Sunday in November.
Any time-dependent product features of ACNS, WAFS or WAAS will be affected by this problem unless you upgrade the software image or apply the workaround as herein described.
Example of potential concerns:
This could cause major problems in your network. If you are using Kerberos in your network, it will fail. Kerberos requires that the time between the client and server be within about 5 minutes. Other authentication devices could also fail when the times are off. It also makes troubleshooting more difficult because the log times are off by an hour.
On August 8, 2005, the Energy Policy Act of 2005 (H.R.6.ENR), was signed into law. Section 110 of this Act modified the time change dates for Daylight Saving Time (DST) in the U.S.
Beginning in March of 2007, DST will begin on the second Sunday of March and end the first Sunday of November.
For 2007 and beyond, the daylight saving time period will be:
2:00 A.M. on the second Sunday in March
2:00 A.M. on the first Sunday in November
For more information on the Energy Policy Act of 2005 please see H.R. 6. (See Section 110)
The IP/TV Broadcast Server (BS) is a Windows box. A Windows patch from Microsoft must be installed for daylight savings time to comply with these new rules. Cisco does not provide Windows patches.
The IP/TV client is an application on a user's Windows PC. A Windows patch from Microsoft must be installed for daylight savings time to comply with these new rules.
Impact to Networking Systems
Networking systems often make use of local time to mark logs, as well as to schedule certain events, such as IP SLA schedule starts, or the beginning or end of a time-based access-list.
In addition, inconsistencies between time zone definitions may impact event correlation systems as well as other management systems relating to problem escalation. Having accurately represented local time is a very big concern for most organizations. Local time may be reflected in logs and on phone displays. This is especially true of systems that require accurate time and time stamping for proper operations.
For networking systems, the clock or clock source is often derived from a trusted chronological source such as a private or public Atomic clock, often through Network Time Protocol (NTP). NTP communicates time in Coordinated Universal Time (UTC), colloquially known as GMT, and thus is not impacted, nor is a workaround for statutory time zone changes. Local time definitions, including summertime settings are part of the configuration of most Cisco products.
Network Time Protocol (NTP) Implications
Regardless of whether or not network components are configured to use differing clock sources, that is, UTC, NTP, and so on, networks will be affected when clock summer-time commands are enabled with incorrect parameters.
Using NTP is not a workaround to this problem. NTP does not carry any information about timezones or summertime settings.
Migrate to a software releases which has the new summertime rules.
A fix has been checked into ACNS 5.5.5 release.
A fix has been checked into WAFS 3.0.9 release.
A fix has been checked into WAAS 4.0.1 release.
The IP/TV PM will require an upgrade to ACNS 5.5.5.
The IP/TV BS and Client get time settings from Windows.
Alternative solution when upgrading is not an option:
You can set the time zone to a generic zone and then create your own summertime settings for that zone. Running the two clock commands noted below on all your U.S. based CE's, FE's and WAE's would:
Change them to a generic time zone with no DST
Add a custom summertime setting that would automatically adjust the clock by 60 minutes on the second Sunday in March and the second Sunday in November.
The following example is for a time zone 5 hours behind Greenwich Mean Time (GMT-5). You would need to specify the offset that is appropriate for your time zone.
clock timezone GMT-5 -5 0
clock summertime GMT-5 recurring 2 Sunday March 2:0 2 Sunday November 2:0 60
The first command sets a generic time zone that does not have daylight savings time associated with it. The second command sets the time back on second Sunday in March at 2:00 A.M. through the second Sunday in November at 2:00 A.M., and changes the time by 60 minutes.
Available patches for other operating systems:
Many of the major OS vendors have already released patches to avoid any problems that the change in daylight savings time can cause. Cisco recommends that you upgrade your OS versions with these patches.
Some of the OS patch-related links are provided below:
Sun Java SE JDK tzupdater Tool
Daylight Saving Time Help and Support Center
IBM-wide product alerts
The change in daylight savings time is sure to affect all Network Management applications that use system time resources. Therefore, Cisco highly recommends that you install these OS patches on all your application servers in order to minimize any impact of this event.
To follow the bug ID link below and see detailed bug information, you must be a registered user and you must be logged in.
Initial Public Release
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:
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