A Modular Architecture for Providing Carrier-Grade SIP Telephony Services

We discuss the development of carrier-grade telephony services in SIP environments. We review available approaches to build SIP applications, introduce a new architecture to provide SIP telephony services and discuss available technologies to implement this architecture. The architecture addresses the modularity, flexibility and scalability requirements for mass-market deployment of telephony services. It is based on the concept of separation between application logic and network functionalities and, at the network level, between signaling and media processing. Parlay, a set of standard object-oriented and signaling protocol-neutral APIs, is used to allow applications to access network functionalities and SIP is used to invoke media capabilities. We have built a soft-switch prototype based on the architecture. We describe the implementation and the lessons we have learned from this experience.