The Design And Implementation Of Softswitch System Based On H.323 Protocol And SIP Protocol

With the development of VoIP, such products based on internet as ip phones are booming and occupying the traditional telecommunication market very soon due to its convenience and low prices. H.323 which was proposed several years ago, satisfies the needs of telecommunication operators and occupies remarkable market quota with its powerful functionalities. SIP which has been developing and burgeoning in the past few years with its simple mechanism and strong extensibility, was ackowledged as the best and comprehensive integrated telecommunication approach of internet.The software switch system is a system for small and medium scale operators. It is developed by Shanghai Weigong Networking and Telecommunication Co. on the account of market needs. It applies a software processing mechanism to implement address mapping and message interaction between H.323 and SIP and establishes communication between two end points to achieve command interaction and to satisfy compatability of these two protocols, and also to extend its application ranges. We first put forward a software switch system architecture for small and medium scale operators according to research and analysis of current telecommunication markets. Then based on the desgin architecture, we implement a stable and efficient system. Furthermore, besides SDP mechanism, we also import XML mechanism to describe media stream information, and thus provides flexibility to media stream description.In the paper, we first look into the background and value of the topic and its research and application situations inside and outside the country. Section 2 and Section 3 describes H.323 and SIP and other relevant protocols in the system where they are used and their address mapping and message interaction. Then, on the grounds of the analysis of system needs and their respective functions, the system is devided into session management module, messagage receiving/sending module, calculating cost module and blog module. Meanwhile, corresponding mechanisms such as message processing and call flowing processing, as well as the design of data base strcutre are explained in Section 4. At last, Section 5 represents how these modules are implmeneted, and the state machine employed in message processing and call flowing mechanism. In addition, the combination of XML mechanism for media stream information description promoted by the practical needs also strengthens the system's functionality and produces an ideal result.