Research And Realization Of SIP Traversing NAT Based On Proxy

Introduction of the author:Li Xuexia, female, was born in September,1985 whose tutor was Professor GuoYong. She graduated from Chengdu University of Technology in communication and information major and was granted the Master Degree in June,2011.With the development of times, information communication technology and Internet technology has undergone tremendous changes, More and more fields began to use the Internet, Meanwhile, the booming development IP nets broadband business and the maturity of VoIP technology applications in the network has dramatically improved the network bandwidth utilization and Greatly reduce the communication cost,but also promoted the development of broadband multimedia applications. Enterprise needs some more and more multimedia features to achieve communication between internal employees not in the same place, such as between branch offices. SIP protocol has become increasingly widespread and popular, Because between the soft-switching and broadband intelligent network server, and softswitch and softphone softswitch is used by the SIP, Its status in the Next NGN (a) can match to the position of No.7 signaling in PSTN or the position of TCP/IP in the Internet. using P2P Hybrid network structure to achieve SIP user registration, query, session establishment, This kind of network structure by P2P and SIP business to carry by SIP(SIP P2P-over-SIP), namely P2P and SIP information exchange between all nodes are accomplished by SIP messages.NAT is the abbreviation of Net Address Translation, maybe they can be seen from the name, it is an agreement responsible for network Address Translation. Popular to say, it is responsible for the private network IP and port within converted into a public network IP and port, that is, we usually refer to IP address mapping. NAT enables an organization in multiple domains reuse registered IP address, before leaving the field,as long as those re-address converting into the global IP address can be solved only registered users to access public network local area network Internet resources, NAT technology depends on establishing a mapping relationship in the network routing equipment of NAT. NAT also has its drawbacks can be overcome, first of all, NAT network throughput will decrease, thus affecting network performance. Secondly, NAT must to translate all address of IP data from the Internet. But most NAT cannot transfer converted address to the IP data loaded, This flaw will cause some to be embedded in the IP address information in datagram load applications such as SIP and other high-level failure. With the development and applications of VOIP technologies, SIP through NAT problems is more and more evident. Although the IPV6 standards have matured, but not completely commercial, before the full deployment of IPV6, research through the NAT SIP protocol has become an important topic, with practical significance.Aiming at the problem of SIP through NAT, analysis and comparison of several NAT mechanism, the final determine using Proxy program in conjunction with the existing environments with enterprise to realize SIP traversal NAT, Analyzed the multimedia information interaction process between network users within the enterprise network and public network or network users within the interaction between the multimedia information. This article describes the implementation and verification program, set up the network environment of the program to do a more objective system of testing, test results show that the scheme can be achieved between the enterprise network and public network transmission of multimedia data, reach the enterprise requirements.