Research On Replication Consistency Maintenance In Unstructured Peer-to-Peer System

With the development of computer technology, especially P2P networks, P2P technology are more widely used in many areas. P2P break the traditional Client/Server model, each node is free to join or leave network in equal status. Each node contributes its own resources voluntarily. Many new applications such as remote collaboration, distributed storage, multiplayer online games are applied to the P2P network. However these new applications give a higher demand on P2P. The traditional read-only file in the P2P network can’t satisfy the requirement. File should be able to read and write, and can be multiple copied. Each user can modify the file, and the modified data should be timely updated to other copies. All of these have higher requirements for file update. The traditional consistency maintenance strategies can’t adapt to high frequency file modification and generate much redundant information in the update process. In this situation, this paper conducts a deep research to the consistency maintenance in unstructured P2P network.On the basis of analysis of previous studies, for the problems of unstructured P2P replica consistency maintenance, a new update strategy, called UPTUR (Update propagation the Tree based on the Update Rate), a propagation tree based on the frequency of update is proposed. This strategy uses Chord protocol as group management Protocol in unstructured P2P networks; all replica nodes of the same file form a Chord ring. An update propagation tree is gradually built by continuous dividing the node space in Chord ring. In order to reduce the update redundancy, we introduces the concept of update rate of a replica, choose the smaller one of file modify rate and replica visit rate as the update rate of replica. Each parent node updates child node according to child node’s update rate to eliminate unnecessary updates and reduce network consumption. In order to reduce the impact of node jitter on the updated tree, this paper also proposed the concept of node stability, giving priority to the node which has higher stability, if the update rate of two nodes is similar while choosing parent node.The simulation results show that the proposed UPTUR strategy can effectively reduce the redundant message in the update process. And the cost of Consistency maintenance is also smaller than the previous strategies in the condition of highly modify rate.