The Study On Improvement Of SoftSwitch Based On Signaling Proxy

With continuous improvement of people's living conditions and the growth in scale of enterprises in recent years, the requirements of global integrated communications have become more and more complex. It's very urgent for global network to integrate together telephone network, computer network and cable television network into one network to meet the requirements of increasing services. However, current PSTN (Public Switched Telephone Network) can't bear increasing tremendous pressure and load any longer. Under such background, a network based on Softswitch technology emerges. It can carry out all the original PSTN services and alleviate the heavy load of PSTN by transferring huge amount of data over IP networks. At the same time, through applying new features of IP technology, the network can bring users rich of new services and enhanced existing services. Hence, it will be possible to carry voice, video, data and other integrated operations over new generation of networks.In 1999, the Ministry of Information Industry enacted YDC 003-2001 (The Technical Requirement for SoftSwitch). It specifies the requirements as follows. Applying the framework of softswitched network and the interfaces of standard protocols enables softswitched network to really become a service-driven network. It adopts the technology of separation control & services apart and separation call-control & carrying apart. So it enable the network operators to choose its own defined service characteristics without confined to network forms and types of terminals and thus improves the flexibility of service development of telecommunications. However, with the application widespread, SoftSwitch also exposes a lot of insufficiencies. Such as, the network security, the transmission equality of pronounciation and the exchagement of many standard protocols equipments.The research subject of this thesis is SoftSwitch. According to the flaws of SoftSwitch in UTStarcom, Signaling Proxy module is designed in the original SoftSwitch to resolve the security and the resource management problems. It is significant on the development of SoftSwitch as well as SoftSwitched network.Firstly, the thesis introduces the concepts, characteristics, main functions, status and development trend about SoftSwitch. Then the thesis brings forward the researchemphasis — overcomes the drawbacks in the security and resource management of SoftSwitch. Secondly, the thesis introduces and compares common VoIP (Voice over IP) protocols, such as SIP (Session Initiation Protocol), MGCP (Media Gateway Control Protocol) and H.248. Thirdly, Signaling Proxy is proposed as a solution based on analyzing the SoftSwitch of UTStarcom in software system and hardware system. The solution proposes to use CPU (Central Processing Unit) load and AS (Application Server) ratio alternative strategies to solve the problem in the waste of AS's resources. It combines non-state proxy mechanisms with B2BUA (Back to Back User Agent) mechanisms to transmit SIP message flow. And it deals with the information flow to protect SoftSwitch and the whole softswitched network. Finally, the Black box testing method is applied to test two main functions — External shielding and load sharing function, and satisfactory experimental data is obtained.