Research On Methodology For SIP Traversing NAT Based On ICE

NGN (Next Generation Network) is the network based on grouping technology, which can provide many services, thus make it applicable in grouping switch net to provide real time voice and multimedia service as a soft switch network. The VoIP(Voice over IP) is just this kind of technology that using IP network to provide the audio and other multimedia communication services. The most popular VoIP protocols are SIP (Session Initial Protocol), H.323. The SIP now becomes the focus of research.NAT (network address translate) is the popular way to solve the lack of IP address, but this technology now becomes the obstacle of SIP. The reason is that the SIP is an end to end multimedia protocol and the IP address of end point must be included in SIP message. How to make the users who having the private IP address communicate is the important problem.The thesis will focus on this problem. In this paper, the generation and development of VoIP and architecture of VoIP based on SIP are all described, and then the call flow and message format of SIP and SDP (Session Description Protocol) are given. After providing the concept of NAT and its categories, the ICE (Interactive Connectivity Establishment) solution for NAT traversal is listed and the advantages, drawbacks for this method are discussed. Then this paper provides a new solution based on ICE. This new solution uses the concept of connection-oriented media transport for reference, and uses the extension of SIP and SDP. It adds some attributes in SIP and SDP, and the parameters of session are described. It sets the priority to these attributes. This new solution can traverse different NAT, and improve the performance of real time communication. Finally this paper simulates this new solution in different environment of Internet. The data include call setup time, end-to-end delay and packet loss rate, and verify the functions of new solution.This new solution bases on client. It can not change the structure of network, and can apply various networks. It solves flexibility and effectiveness of NAT.