Design And Implementation Of Soft-Switch Based SIP Gateway

In the era of rapid development of telecommunications technology, based on the traditional PSTN (Public Switched Telephone Network), telecommunications network has been unable to meet the needs of customers; on the other hand, the traditional telecommunications carriers and internet services providers want to integrate the low cost, non-carrier-class, less reliable VoIP (Voice over IP), instant messaging and other new technologies into their telecom business services. For equipment providers, they also want to provide a complete set of solutions and hardware equipment for enterprise customers. To meet these requirements, NGN (Next Generation Network) was born and evolved. NGN has been developing fast in recent years, but also encounters a number of challenges. The biggest one is the difficulties to connect a variety of media gateways, signaling gateways, smart terminal, media servers, etc. to NGN network. However, considering the lack of IPv4 address resource, many companies use private network in their office. Normally, these terminals or servers which have private IP address are difficult to be reached by external users or applications. Meanwhile, these companies plug in a firewall on the bridge between internal and external networks to protect the internal resources, thus further increasing the difficulty of company's internal and external interconnection for voice and video communications. Therefore, a mature, low-cost solution is a mandatory and urgent requirement.Under this background, this paper studies various ITU, IETF protocols and Soft-Switch platform, and designs a SIP based Soft-Switch platform. Furthermore, based on this platform, it compares the popular firewall traversal solutions in NGN environment, proposes and implements an intelligent, low-cost, safe, higher extensible gateway which is based on SIP and its cluster. The gateway helps customers solving the access problem in NGN network, protecting their existing huge investment on network security products, and provides flexible expansion capabilities to integrate into other AAA systems seamlessly.Detail works of this paper include: 1) Developing a SIP-based soft-switch platform to support voice, video and text communications ;2) Analyzing the existing firewall traversal solutions under NGN network, and then proposing a SIP soft-switch based, intelligent, secure SIP gateway solution;3) Based on the solution, analyzing, designing and implementing a SIP gateway. SIP gateway functional requirements and non-functional requirements are analyzed. Static model, dynamic model, data model, security, and error handling are designed. The gateway goes through the application layer to control the firewall to meet customer audio and video communications requirements, and can interoperate with the soft-switching platform, intelligent terminals, SIP servers. Furthermore, taking the benefits from PKI, the gateway can provide a higher level of secure access control;4) Conducting functional testing, performance testing, stability testing and safety testing on SIP soft-switch platform and gateway. Finally, the platform and gateway are test-running in a government office network.Testing results show that SIP gateway and soft-switch platform reach the original goal, and can meet business requirements of secure voice and video communications.