Implementation Of The NAT/FW Traversal Technology Based On TSM

Along with the mobile communication technology and network information technology development, the new manner and service of communication have begun to emerge to the vast media and numbers of users constantly. IMS (IP Multimedia Subsystem) multimedia subsystem is a kind of new multimedia business form, which is considered to be the Next Generation Network (NGN) core technology. Also, IMS is an important way to solve the problem of the FMC (Fixed Mobile Convergence), the introduction of triple integration in voice, data, video and other differentiation of services. It can satisfy the requirement of more innovative and diversified multimedia services to terminal users. However, the main problem of SIP (Session Initial Protocol) protocol adopted by IMS in the transmission among the different networks and the security of communication, need to be resolved, at present.This paper is combined with the tunnel protocol TSCF (Tunneling Service Control Function) which is provided by the Acme Packet Company and TLS protocol based on OpenSSL (Open Security Socket Layer), the traversal of NAT (Network Address Translator) equipment and firewall in the network is achieved. Whilst, the security of communication in SIP protocol between the users can be guaranteed, which lay the technical foundation for IMS popularization and application.The mainly work of this paper is listed below.(1) The requirement analysis about this project is combined with the conclusion of the discussion which I participate in with Acme Packet TSM team and NCS (Nokia Siemens network Communication Suite) project team, and the knowledge during the time of study in person. According to the analysis of SIP protocol adopted by IMS system, and the existent NCS communication system, a proposal of complete functional requirements and performance requirement is presented by this paper.(2) The summary design and detailed design of TSE (Tunneling Service Element) function module has been finished, which is mainly referenced with the tunnel protocol, TSCF, introduced by Acme Packet Company, and TLS/DTLS protocol based on OpenSSL toolkit.(3) The realization of communication with encryption and decryption is followed by TLS/DTLS protocol based on OpenSSL. Some complex function points and the interface calling programs of TSE module were implemented using by C/C++.(4) The TSE module has been embedded in NCS communication system, so that the NCS is equipped the function of the NAT/FW traversal.This proposal has been used in Nokia Siemens Network Company through the tunneling traversal mode, which can be satisfied the most basic communication requirement of internal workmate which include VoIP, Voice Conference, Video, IM.