Research And Implementation Of The NAT/FW Traversal Technology Based On ICE

With the popularization of computer technology and Internet technology advances, the requirement of multimedia data such as voice and video transmission has also gradually increased. VoIP has more and more extensive range of applications. But in the current IP network, lots of NAT/FWs have been set up, which have become to the impediment to VoIP business application. Therefore, traversal through the NAT/FW technology still has much value of research.Recently, ICE combines the advantages of other methods, ensures the feasibility and scalability of traversal. But ICE will completely use the TURN method but can not able to use P2P method when traversing Symmetric NAT. In this respect, this dissertation does the main in-depth study.Based on the above issue raised by, first, this dissertation describe the NAT principle and the classification of NAT in detail, makes an intensive study of the limitation reasons of NAT for VoIP data and describe the UDP Hole Punching technology process in detail.Next, This dissertation studies the characters of Symmetric NAT and find linear regularity of port distribution of Symmetric NAT. Based on it, this dissertation puts forward P-PRE port prediction algorithm, redesigns the ICE message protocol, makes improvements of the deployment of ICE server, the process of address collection, the priority order of address and connectivity check process. Based on these improvements, this dissertation puts P-PRE algorithm applied in the ICE process, which makes ICE utilize the P-PRE algorithm to establish P2P connection and traverse Symmetric NAT.Finally, this dissertation combines the VcomOffice2008 video conference system, realizes the ICE protocol and does a lot of tests in different network such as enterprise local area network and public network. Test results show that optimized ICE program has 78 percent of probability to establish P2P connection when traversing Symmetric NAT.