Prototyping softswitch with an emphasis on protocol relationships

Taking the prototype of a class 4 (C4) softswitch developed in Beijing University of Posts and Telecommunications as an example, this paper discusses the complexity of softswitch because of its multi-protocol property. How to deal with the protocol relationships in each protocol group or between different protocol groups are discussed. Furthermore, other issues such as design of generic protocol data unit (PDU), design of generic call control model, generic service control model and generic call bearer control model are studied. The extensibility and availability of softswitch are also under consideration. Based on a mechanism of session initiation protocol for telephony (SIP-T), the information translation mode and information encapsulation mode are jointly used widely in the PDUs of 5 classes of generic protocols, by which the high efficiency of system and integrality of information are ensured. The guide of protocol relationship and protocol grouping is proved significant. This paper may be a good reference to develop other softswitches or similar products