Research On SBC In SIP-based VoIP And Implement Of Its Key Module

The development of the computer network technology has brought tremendous changes in all aspects of the world, and VoIP telephony which based on IP network offers a new way to far distance communication among the people with low price. And the new-generation VoIP network based on multimedia communication appears with the birth of SoftSwitch technology.But VoIP has also met some problems in the developing process, which hinder the VoIP further development. These problems mainly are:①Network Address Translator (NAT) and firewall technologies,which are used for solving the shortage of IP addresses and the issue of network security, have block the end-to-end communication.②Identity authentication of access device.③Configuration and management of access device.④The problems of VoIP network security.⑤VoIP QoS(Quality of Service) problems.In view of the above problems, the Harbour Networks Limited Company, as a telecommunication equipment supplier, solved the problems from the network layer, promoted a new solution, using Session Border Controller based on the ITCP (Intelligence Terminal Convergence Protocol)--ITCS (Intelligence Terminal Convergence System) solution, provided a new networks strategy choice for telecom operator.The ITCS solution is not merely to solve the NAT/firewall traversal and achieve network end-to-end inter-communication without the barrier; it also can solve the problem of the access equipment registration and authentication, the problem of the access equipment management and configuration, the problem of VoIP network security etc.The author participated in Harbour Network ITCS project, summarized theories and practices during ITCS server part developing process, and completed this dissertation after the research of VoIP system.The main research content and the work achievements of the dissertation have the following several aspects:①Analyzed the VoIP technology principle and development, and carried on theoretical study to the VoIP key problems. VoIP still has a series of problems need to be solved although it developes rapidly, like the NAT/firewall traversal, the QoS(Quality of Service) problem, VoIP network security problem etc, the three problems have been studied thoroughly in this dissertation.②Analyzed SIP Protocol used by VoIP communication system which based on soft-Switch technology, and took a detailed analysis of VoIP call flow and SIP end-to-end communication problems under NAT combining with SIP Protocol.③Carried on the research on the SBC communication model and the SBC work principle, and took the analysis from the communication channel layer and the conversation layer.④In view of the problems of VoIP encounted , the dissertation presented SBC solution which based on ITCP protocol---ITCS solution, The solution commendably solved the above problems working with ITCP protocol cluster. the dissertation introduced the design of ITCS system and realization mechanism of its main functions. Because the ITCP protocol is the foundation of the ITCS solution, and took a detailed explanation of the ITCP protocol stack design in the fourth chapter.⑤Finally emphatically introduced software design and implementation of SIP module, which is responsible by author, and did the function and performance test and analysis of the SIP module.The ITCS solution commendably solved the problems of current VoIP encountered in the case of not changing any equipment of network transportation (switch/router/NAT) or Firewall. The experimental bureaus of the solution's commercial products have been opened in Yunnan and HongKong and received the good effect, provided the help of VoIP large-scale application.