Phone Time with CUCM 7.x SCCP

Unanswered Question
Mar 8th, 2011

I have been battling with this for some time.   Our Phones continuously slip by a few minutes.  Where do they pull the time from?  OS of CM?  We are not using NTP references in our Date/Time groups.    Our PC's and mobile devices are always in sync...windows uses the native time service and mobile devices obviously use the carrier network.   Any suggestions on what to check?

I have this problem too.
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Anthony Holloway Tue, 03/08/2011 - 15:43

What phone/firmware is this for?

The phones use the Date/Time Group in the Device Pool setting for their time.  If no NTP refs are populated, then the CUCM time is used.  Do your CUCM's point to an NTP?  You can check in OS Admin.

Here is a note from the 7965 Guide:

The Cisco Unified IP Phone displays the date and time from Cisco Unified Communications Manager.

If the Cisco Unified Communications Manager server is located in a different time zone than the phones,

the phones will not display the correct local time.

james.procopio@... Wed, 03/09/2011 - 09:55

Anthony,

Appreciate the quick reply.   The phone are mostly 794x's running SCCP.   Althought the date/time group does not use any NTP references, the OS Admin shows a NTP server defined, one of which I am not confident we should be using.  If I remove this, then technically I should be able to control the time feom CUCM and that is what the phones will receive...correct?

james.procopio@... Wed, 03/09/2011 - 09:54

Anthony,

Appreciate the quick reply.   The phone are mostly 794x's running SCCP.   Althought the date/time group does not use any NTP references, the OS Admin shows a NTP server defined, one of which I am not confident we should be using.  If I remove this, then technically I should be able to control the time feom CUCM and that is what the phones will receive...correct?

Cedric Van Labeke Thu, 03/10/2011 - 14:38

Hi James,

SCCP phones get their time updated from ccm process each time there's an on-hook/end call event.

It takes server time and DateTime Offsets into consideration. Do keep in mind what the design guide recommends in terms of stratum for NTP sources.

"Cisco highly recommends  configuring the publisher to point to a Stratum-1, Stratum-2, or  Stratum-3 NTP server to ensure that the cluster time is synchronized  with an external time source.

Cisco recommends synchronizing Unified CM with a Cisco IOS or  Linux-based NTP server. Using Windows Time Services as an NTP server is  not recommended or supported because Windows Time Services often use  Simple Network Time Protocol (SNTP), and Linux-based Unified CM cannot  successfully synchronize with SNTP.

The external NTP server specified for the primary node should be NTP v4  (version 4) to avoid potential compatibility, accuracy, and network  jitter problems. External NTP servers must be NTP v4 if IPv6 addressing is used."

-- http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/8x/netstruc.html#wp1185637

The NTP references in the date/time group would be more used by SIP devices. These will go and talk to the NTP servers instead of being updated by CM.

Cheers,

Cedric

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