Research And Realization Of Solution For NAT Traversal In P2P Communications

The application of P2P communication mode in internet makes the communication and interaction among the users more directly and conveniently. Currently, a serious lack occurs in IPv4 address as the internet users increase quickly. The appearance of Network Address Translation (NAT) equipments has solved this problem. While the IP address of the hosts behind the NAT are invisible in the Internet, therefore such hosts are inaccessible for those hosts in the Internet, even though a P2P network requires direct information changes between peers. It has made difficulties for connection using P2P protocols. How to solve the problem of NAT traversal in internal and external network of P2P communication becomes an import issue in network communication area.This paper researched several different types of NAT traversal techniques and promoted a P2P communiction method based on TCP NAT traversal. The paper contains the following information:First of all, this paper introduced the concepts, principles, categories, configuration management and impact of NAT to communication. It then introduced the concept of P2P and analyzed features of P2P networks, applications and structures of P2P network.Secondly, this paper gave detailed illustration to the key techniques of NAT traversal, analyzed several popular NAT traversal techniques and summarized their advantges and limitations.Thirdly, it promoted a technique of NAT traversal based on TCP. This solution could establish trustworthy TCP connection between two computers that locates behind Firewalls/NAT under the assistence of servers. This paper gave specific steps and demonstrations of this solution and proved the feasibility by theoretical analysis.Finally, this NAT traversal model based on TCP was implemented in Visual C++. It successfully established connecton between two NAT hosts. This experiment further proved the feasibility. Success rates were analyzed in the experiment.