一种非DHT查找方式的结构化P2P文件共享模型

普遍认为在结构化P2P协议中实现能力感知会增加网络开销.提出一种能力感知结构化P2P协议——HeteroChord，HeteroChord在新加入结点的路由表建立算法与更新算法中实现能力感知，能力感知速度快，在动态环境下，HeteroChord具有比Chord更小的维护开销.针对HeteroPastry文件索引双向复制开销大以及不能遍历强结点的缺点，以HeteroChord协议为基础建立一种非DHT查找方式的文件共享模型——NHFS，NHFS将超级结点简单首尾相连形成super leaf set，并采用选择性单向复制把文件索引复制到超级结点，使查询仅在超级结点中进行.super leaf set使查询可以方便遍历超级结点，且选择性单向复制文件索引产生的网络开销远小于双向复制文件索引产生的网络开销，相对HeteroPastry而言，NHFS文件共享模型更合理.

A Structured Peer to Peer File Sharing Model with Non-DHT Searching Algorithm

It is commonly believed that extending structured peer to peer overlays to be capacity-aware will increase maintenance overhead, so it is significant to build a capacity aware protocol that is effective and has low maintenance overhead. Presented in this paper is an effective capacity-aware structured peer to peer protocol—HeteroChord. HeteroChord does not use the traditional method of nodes exchanging routing information to implement capacity awareness, it implements the capacity aware mechanism in a new node’s joining algorithm and updating algorithm. Compared with traditional capacity aware protocols, when a new node joins the system, HeteroChord can calculate the nodes whose routing table should be updated, so the capacity aware mechanism is efficient. The simulation results indicate that the maintenance overhead of HeteroChord is less than that of Chord under churn. Then a non-DHT structured file sharing model called NHFS is constructed based on HeteroChord. In NHFS, The supernodes are connected by super leaf sets, and the file indices are replicated to supernodes, so the queries can be processed simply in supernodes. Super leaf set makes it easy for the queries to traverse the supernodes in NHFS, and the maintenance overhead generated by unidirectional replication mechanism in NHFS is much lower than that generated by bidirectional replication mechanism in HeteroPastry. So the file sharing model NHFS is more reasonable than HeteroPastry.