Methods, systems, and computer program products for clustering and communicating between internet protocol multimedia subsystem (IMS) entities

Methods, systems, and computer program products for clustering and communicating between Internet protocol multimedia subsystem (IMS) entities and for supporting database access in an IMS network environment. According to one aspect, an IMS cluster node includes a serving call state control function (S-CSCF) for controlling media sessions between IMS users. The cluster node further includes a home subscriber service (HSS) function for storing and providing IMS subscription information to the S-CSCF function. A shared memory is operatively associated with the S-CSCF function and the HSS function. The S-CSCF function obtains IMS subscription information from the HSS function via the shared memory.