Research On The Controlling Strategy Of Avoiding Free-riders In P2P Networks Based On QoS

In recent years, with the development of computer and network technology, P2P network have been more and more applicated in the field of file sharing and information searching. However, the free-rider phenomenon and poor quality of tranaction resource make badly effects on toughness and efficiency of P2P network. The design philosophy of P2P network is to improve the network efficiency, use the network resource fully, develop the potential of each node as possible as it can. So this paper make research in inhibiting free-riding behavior and improving the quality of tranaction resources.This paper firstly proposes a new balance mechanism aiming at "free rider" phenomenons in peer-to-peer network, which promisses free-riders existence in certain degree and encourages nodes to particpate in sharing resourses with other nodes in the network activily. Simulations results prove that this balance mechanism is able to use network resources effectivly, and it also can restraint serious free-riding behavior inhibition.Next, this paper proposes a model based on trust value of nodes against vulnerability, which not only takes into account the node's connections, but also gives full consideration about the node's trust value. In accordance with the type of pre-transaction resources, selects nodes that have higher trust and fewer connections to make transaction. Simulation proves that this model can avoid generating hubs effectively, improve the ability to defend against coordinated attacks, and also enhance the network robustness and stability.Lastly, this article proposes a new strategy that bases on quality, size and number of file to avoid the phenomenon of free-rider. In the new strategy, we can obtain nodes' effective contribution values in according with the nodes'trust values and contribution values, and select the node that has bigger trust value as service provider node. Moreover, the network can be divided into several domains according to the physical distances between nodes in the network. Simulations prove that this strategy can guarantee the quality of service as well as restrain free-rider phenomenon, so as to enhance the utilization of resources and the rate of successful transaction.