Why would I use a Cisco 7900 phone on CUCM using SIP?

There’s not much of a compelling reason to use the SIP binary image on the Cisco 7900 series phones if you’re using Cisco Unified Communications Manger with the phones. If a company was using a Cisco 7900 series phone registered to another vendor’s PBX, converting the phone to SIP would make more sense. Most vendors support SIP line side support, but do not support the Cisco proprietary Skinny Client Control Protocol (SCCP) that runs by default on the 7900 Series phones. When using CUCM, the full CUCM telephony feature set will work with SCCP and a Cisco Type B phone. Type A phones do not support some of the features added beginning with CUCM versions 4.2 and 6.0. As an example, the Intercom feature is not supported in either SCCP or SIP on Type A phones. Type B phones support all CUCM features in both SCCP and SIP with some minor exceptions that we will go over. The following is a list of many of the Type A phones: 7910/7902/7905/7912/7940/7960 The following is a list of many of the Type B phones: 79×1/79×2/79×5/7906/7970 Now let’s go over a couple of scenarios in which we would need to use the SIP binary load on a phone when registered to CUCM. #1 Cisco Telepresence – Cisco Telepresence uses a 7975G phone with a SIP binary image load. The Cisco Telepresence solution requires the SIP binary image set. #2 SIP Dial Rules – SIP dial rules can be downloaded to SIP phones. This feature is not supported with SCCP based phones. SIP dial rules will allow a class of service (CoS) deployment in which the endpoint makes the permit or deny decision for each call based on a local dialplan file downloaded to the Cisco SIP phone as part of the registration process. SIP dial rules can lower post dial delay in deployments where CUCM is geographically very far away from the endpoint (Cisco phone). A phone in California may suffer some delayed dial tone and post dial delay if it is registering with CUCM in Dubai (or vice versa). #3 Only 42 lines are available on a phone with SCCP. The 7915 and 7916 modules support up to 24 lines each, and two of the modules can be used on the same phone. 796x phones with two 7915 modules can support up to 54 lines (6+24+24); while the 797x phones can support up to 56 lines (8+24+24) with the 7916 module. The SIP binary image can support all lines in these scenarios. If there are any other features that would require Cisco SIP phones when registered to CUCM, please post some comments and share.