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

With the development of the network technology, especially peer-to-peer technology in recent years, unstructured P2P technique is gradually applied in newly-developed cooperation computing systems. The typical newly-developed applications include trustable management, directory service, online games, remote collaboration and so on. In these kind of applications, owing to data is shared and copied in many peers, and could either be read or written by any user, update behavior would frequently occurs in the systems. An efficient consistency maintenance method is so important to the newly-developed applications that the applications could only offer static data sharing without the method. So the development of new applications needs an efficient consistency maintenance method to support the frequent updata behaviors.The new applications require not only strong consistency, but also fast propagation of update messages. So this paper conducts the thorough careful research to the consistency maintenance method for unstructured P2P systems.Based on analysis and comparisons for existing methods, the author proposes a novel consistency maintenance method for unstructured P2P systems, named HSUPTL(High Stability Update Propagation Tree with a Lifetime). This method puts the replication node of one file into a group, uses Chord as the group management protocol. The update messages are propagated along with a tree which is built by the partition of ID space of Chord ring and the head node selecting from the corresponding region. To reduce the redundant update messages, this paper proposes "Instantaneous Stability", put the node whose instantaneous stability is larger near the root when building the update tree; to reduece the cost of the maintenance of update tree, this paper proposes "lifetime", limit the time to live of the update tree.Theoretical analysis and simulation results demonstrate that this method is more efficient in maintaining replica consistency and updating replica nodes with less costs and redundancy messages for unstructured P2P systems, especially when the update behaviors frequently occur.