Abstract: Unstructured Peer-to-Peer（P2P） systems are largely self-organized and scalable.However，the loose overlay structure and the mechanism of a peer randomly joining and leaving a P2P network cause topology mismatching between the P2P logical overlay network and the physical underlying network.Meanwhile，due to the inefficient overlay topology，the flooding-based search mechanisms cause a large volume of unnecessary traffic.Aiming at alleviating the mismatching problem and reducing the unnecessary traffic，the dynamic overlay topology optimization technique is proposed.The algorithm gets the current topology information through flooding queries among peers so as to alleviate the mismatching problem involving the optimization policy.

摘要： 无结构P2P（Peer-to-Peer）系统的自身结构特征表现着良好的自治性和扩展性。然而，由于自身松散的重叠网拓扑结构以及对等节点可以自由地加入和离开的特点，系统十分容易产生重叠层与底层物理网络的拓扑结构不匹配的问题。另一方面，由于无结构P2P系统大多数采用泛洪式转发，大量的消息会通过低效地重叠网连接占用带宽，产生不必要的数据冗余，从而影响网络的性能，降低整个网络的利用率。提出一种动态拓扑优化模型机制，该机制通过节点在消息转发过程中获取实时的网络拓扑信息，进而通过一系列优化策略对低效的拓扑结构实施优化。