An Application Router for SIP Servlet Application Composition

The SIP servlet standard offers a familiar Java application programming interface (API) for developing session initiation protocol (SIP) applications, and the upcoming version 1.1 specification standardizes how multiple SIP servlet applications are composed and invoked to service a communication episode. Such disciplined composition promotes software modularity and reuse, and also helps manage feature interactions. At the core of the application composition framework in the SIP servlet API 1.1 is the Application Router that performs the task of selecting an application to service a SIP request. In this paper, the authors describe an application router implementation based on the distributed feature composition (DFC) architecture routing algorithm (DFC-AR). While the DFC-AR is designed to be simple so it can serve as a sample implementation, it is also sufficiently powerful for real-world VoIP service deployments. The DFC-AR has been proposed to be the default AR in the reference implementation of the 1.1 specification.