Research And Application Of NAT Traversal Technology Based On STUN Protocol

NAT technology alleviates the shortage of IP address resources and strengthens the security of intranets.However,the use of NAT technology also makes P2 P communication very difficult.The NAT technology makes the internal network host and the external network host unequal,so they can not establish a peer-to-peer connection,which seriously affect the application of P2 P communication.Therefore,P2 P applications must solve the NAT traversal problem so that any host can establish peer-to-peer connections and communicate with each other.Aiming at the shortcomings of the existing NAT traversal technology based on the STUN protocol,corresponding improvement plans were proposed and implemented in this thesis.And a new port prediction method was proposed for Endpoint-Dependent Mapping NAT traversal.To solve the problem that a single NIC server cannot provide complete STUN service,a single NIC server combination scheme is proposed.And on the basis of this,a pairing server selection strategy and a load balancing technique with adaptive load indicator weights are proposed.Finally,the improved scheme is applied to the actual smart home project,conducted test analysis.The work done by this thesis is as follows:1)Analyze the principle of the detection flow of NAT behavior,and point out the problems of misjudgment and time-consuming problems,and propose improvements.In addition,by modifying the communication flow between the client and the STUN server,the detection time of Address and Port-Dependent Filtering NAT is greatly reduced.2)Analyze the traversability and traversal processes between different NAT types,analyze in depth the impact of port unreachability problems on NAT traversal,propose an improvement scheme,and propose a new port prediction scheme for Endpoint-Dependent Mapping mapping NAT.Design the overall flow of NAT traversal based on the above improvement scheme.3)A NIC server combination scheme is proposed to provide a complete STUN service externally,and a corresponding matching server selection strategy is designed.In addition,in order to implement load balancing effect of STUN servers and forwarding servers,based on the analysis of the deficiencies of the existing dynamic load balancing algorithms,a load balancing strategy with adaptive load indicator weights is proposed.4)The above improved scheme is applied to an actual smart home project,and a test analysis is performed to verify the actual availability of the improved scheme and the NAT traversal effect.Practical application shows that the improved NAT traversal technology based on STUN protocol in this thesis can effectively reduce the time of NAT behavior detection,improve the NAT traversal rate,and have a good NAT traversal effect,which has certain application value.