| The Session Initiation Protocol (SIP) has been widely used in the Voice over IP (VOIP) network, and the related technologies are becoming increasing mature. But due to the multi-protocol heterogeneous environment and the diversity of its realization, the expansion of the SIP module in particular server system still has high technical complexity. So how to implement a lightweight SIP server which has a good software architecture, high scalability and flexibility, becomes a more and more important issue in the VOIP network.First the basic concepts and key technologies related to VOIP and SIP were expounded, and then the SIP protocol architecture and the basic framework were systematically discussed. On this basis, this paper presented an in-depth study of the SIP-based server, considering its communication model and software architecture. The SIP server model implemented in this paper is composed of five modules which have high cohesion and low coupling. Functionally, from top to down, the modules include I/O interface module, SIP channel module, public channel module, PBX module and application module. With a compact software structure, the system has provided the following major functions: client verification, authorization registration, session establishment and removal, media interchange through the server. Generally speaking, the system makes a complete realization of the SIP protocol.Finally, a user-case testing plan for the implemented SIP server system is given, which makes a full-round verification into the server function and its performance. The system this paper implemented can be used as an independent VOIP server or an extended SIP module. |
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