End hopping is one of the good methods to defend against network attack,but has problems with network address translation（NAT） because packets sent from an unknown endpoint would be dropped by NAT.To avoid the dropping of packets,we propose a punching scheme：a client sends a punching packet to create mapping rules in NAT,so that the packets from the server would be able to pass through effectively with such rules.In this paper,some preliminaries and definitions are provided for building the model of end hopping.Then we discuss the main reason of such packet dropping and specify all the failure situations based on the model.What＇s more,we analyze how the punching scheme helps end hopping cross NAT.Finally,we validate the feasibility of this scheme with empirical results：if the client is behind a NAT and with punching scheme,the service rate increases to 100%.Therefore,our proposed scheme can greatly improve the performance of crossing NAT in end hopping with little security and computational overhead.
This paper proposes a simple and efficient distributed algorithm for calculating minimal dominating set in wireless sensor network. This method can avoid maintaining the connectivities between backbone hosts. Considering that the hosts in mobile networks have different characteristics, this paper proposes a method of calculating minimal dominating set with weight. The nodes can be chosen to form a minimal dominating set when the network topology changes. For the host switch on/off operation, the updating algorithm was provided. The change in the status of a hostaffects only the status of hosts in the restricted vicinity. Simulation results show that the proposed method can ensure fewer dominators but with higher weight to form the minimal dominating set and the nodes can be adaptive to the changes of network topology.
