The Design And Implementation Of A Nat Traversal Solution On Session Border Controller

Voice over IP technology which is based on IP network develops with the rapid development of network applications. The most important advantage of VoIP is that it can make use of the global IP internetworking environment, to provide cheaper and more extensive voice services than traditional PSTN telephony. At the same time, as SIP has more advantages than H.323, More and more VoIP systems are implemented with SIP instead of H.323.The wide application of VoIP greatly increases the demand of IP addresses, but NAT and firewall technologies, which are brought forward for the insufficiency of IP address and the network security, conduce to issue between end to end communications. Consequently, how to solve the problems mentioned above effectively will greatly affect the promotion and application of VoIP.Session Border Controller is a new network device of VoIP access layer. It can solve the problem of NAT traversal by controlling the VoIP sessions on the network border. At the same time, it can control bandwidth, manage sessions and make traffic statistics.This thesis focuses on the research of the NAT traversal solution on SBC. Firstly it analyses the related protocols in SIP-based VoIP system, introduces the NAT technology and some NAT traversal solutions. Then, the thesis mainly illustrates the NAT traversal solution on SBC. Theory and realization details of the solution are described in this paper. Finally, basing on this solution, we design and implement the SBC prototype system; in addition we test its function and capability. The result demonstrates that the function and capability of the system reaches our expectation. The SBC prototype system has fulfilled the requirement of SIP traversal NAT. It will be a good help to wide usage of VoIP application.