中文摘要：

NAT（Network Address Translator）不仅解决了IP地址短缺的问题,而且也使内网主机避免了来自网络外部的攻击。但对于P2P应用来说,需要建立端到端的连接,所以说如何穿透NAT成为了P2P技术中的一个关键。通过对当前NAT穿透技术的研究,发现依靠TURN（Traversal Using Relay NAT）来实现对Symmetric NAT穿透往往存在服务器负担重、延时、丢包的问题,于是给出一种基于端口预测的NAT穿透新方法。该方法避免了依靠TURN来实现对Symmetric NAT穿透所带来的难题,大大满足了对网络安全要求高而使用对称型NAT企业的需求。

英文摘要：

NAT（ Network Address Translator） not only solves the problem of IP address shortage,but also makes the network host avoid the attacks from outside the networks. But for P2 P application,it needs to establish an end-to-end connection,so how to realise NAT traversal becomes a key in P2 P technology. Based on the research of current NAT traversal technology,we found that to achieve Symmetrical NAT traversal relying on TURN（ Traversal Using Relay NAT）often has the problems of heavy server burden,time delay and packet loss. Therefore,in this paper we present a new NAT traversal method by using port prediction,the method avoids the problems brought by relying TURN to implement traversal of symmetrical NAT,and greatly satisfies the requirements of those enterprises who have high demand on network security and thus use symmetric NAT.