Blending of external applications with advanced telephony services in the IP Multimedia Subsystem (IMS)

Advanced feature servers are at the core of enterprise IP telephony, offering traditional services, such as call hold, voicemail and find-me-follow-me. These feature servers have begun to be deployed as IMS Application Servers to support both in-house (premises based) or hosted service (IP Centrex) offerings. At the same time, there exist applications that are external to IMS that can provide a richer communications experience, when integrated. The application layer in IMS allows these external applications to be blended with the advanced telephony features. An example of this is the use of Microsoft Office Communicator for call control. Several current implementations integrate this feature through a back-end proprietary interface to specific feature servers. We present an architecture for generalizing this integration with a CSTA/IMS gateway that can interact with any IMS feature server.