Abstract: Methods, systems, and computer program products for clustering and communicating between Internet protocol multimedia subsystem (IMS) entities are disclosed. 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.

Abstract: Methods and systems for routing messages between a core network and a radio network controller are provided. A radio access network gateway translates messages from an ATM-based protocol to a non-ATM-based protocol, such as the stream control transmission protocol and vice versa. The radio access network gateway forwards the SCTP messages to the core network. In addition, the radio access network gateway receives messages from the core network formatted according to the core network protocol and translates these messages to an ATM-based protocol for communication to a radio network controller.