Research On The Controlling Mechanisms For Avoiding Generating Hubs In P2P Networks

The existence of the hubs in Peer-to-Peer(P2P) network could greatly increase the network's vulnerability and blemish the performance and the quality of P2P system. This thesis firstly introduces the measurements of hubs in P2P networks in recent years and gets to the result that the existence of hubs is a characteristic of P2P networks. It also summarizes two kinds of controlling mechanism for hubs, the topology control and free-riding restraint.Because the researches about hubs are mainly in restrain mechanisms of free-riding, the second section of this thesis presents and also analyses the presented restrain mechanisms. In order to eliminate the defections of these restrain mechanisms, this thesis gives out a fair utility function by taking into account the absolute contribution and physical performance simultaneously while calculating the utility value. The absolute contribution is divided into two part, supply value and profit value. With Analytic Hierarchy Process, we build the supply value model, profit value model and physical performance model, and then we settle the fair utility function by calculating these models to resolve the problem of unfair utility value. Building on this result, we produce an indirect controlling mechanism of hubs in P2P networks with pyramidal rank structure based on free-riding restraint measurement. In this mechanism, each user has a rank according to its contribution and it can just visit the corresponding rating files with its rank in the system. Users can set and manage the ratings of their sharing files autonomously. The rank structure is pyramidal to enable that the problem of hubs would be solved by user's self-management. This controlling mechanism also can solve the problems of the QoS of new users, the over strictness and the unopened punishment.Lastly, this thesis presents a new model to avoid generating hubs in the networks by controlling the logical topology of P2P networks. This controlling model is to hierarchize the becoming hubs. The becoming hubs should search in the network and choose out two standby nodes by using the concept of remainder capacity of supporting more connections. The becoming hubs and the standby nodes must be made into a binary tree logically. When comes the new request, the becoming hubs could transmit the request to one of the two standby nodes with the rule of IP address margin. This controlling model can control the hubs and avoid generating the hubs in P2P networks effectively.