Research On Replicas' Consistency Maintenance Based On Unstructured Pure P2P System

As the Internet's development, the technology of P2P network is being given more and more attention and researches. Various applications based on P2P technology are showing up. People don't satisfy with functions which are intended for searching and downloading all kinds of resources. Many P2P systems supporting dynamic businesses have become new research objectives and directions.The technology of replication raises some problems when it increases the reliability and usability of distributed systems as a vital technology. One of the most important problems is how to maintain the consistency of the replicas. Thus, the research of replicas' consistency on P2P platform is very meaningful.This thesis analyses typical algorithms of keeping replicas' consistency and points out their drawbacks. Moreover, this thesis comes up with a novel consistent algorithm which can improve the performance and efficiency of delivering update messages. This algorithm is called Replica Chain Based Consistency Maintenance Algorithm. It utilizes the broadcasting of probing message to create a replica chain of a file after the initial node collects response messages from other replica nodes. After the chain is constructed, update messages will be transferred through it without flooding blindly. And the maintenance of the chain is facilitated by the broadcasted message recorded by every node receiving it. Experiments with the algorithm on the PeerSim platform compared with flooding algorithm show that it is effective. Besides, this thesis provides two methods to avoid conflicts and applies one of them to design a simple prototype system which is based on the replica chain algorithm.