基于衰落Bloom Filter的P2P网络弱状态路由算法

摘要

The current weak state routing schemes cannot facilitate in-network queries effectively. When a query is given for an item at an arbitrary node, disturbance in unrelated routing entries are likely stronger than the useful information in the right routing entries. Consequently, the majority of queries are moved towards wrong nodes. To solve this problem, this paper presents Dwalker, an efficient weak state routing scheme-based design based on decaying bloom filters. Dwalker uses a bloom filter to represent the summary information of resources at each node and then propagated a bloom filter within a propagation range. The amount of information in each bloom filter decreases exponentially with the distance from the source. Dwalker makes the max propagation range less than the expected distance between any two nodes; hence, effectively tackling the problem of multi-path propagation of a decaying bloom filter. Dwalker replaces a single bloom filter with multiple bloom filters as a routing entry and holds more routing information. Dwalker can ensure that any query can be forwarded in the right direction with high a probability that is based on the proportion of bits set to 1 in a bloom filter and the least number of bits set to 1 in an entry bloom filter for a query. The analysis and simulation of results show that Dwalker can make many queries that can be forwarded in the right direction to achieve a high query hit rate with low cost and low delay.%在P2P网络中,基于衰落Bloom Filter的弱状态路由算法试图将每条查询消息沿着成员资格信息量最强的方向传递,并最终以较低的传输代价和传输时延确保较高的查准率.衰落Bloom Filter在传递过程中存在严重的多径叠加和噪音问题,这直接导致查询消息会以很高的概率沿着错误的方向传播,甚至会退化为泛洪路由算法.为了解决这一挑战性难题,提出了DWalker这种基于衰落Bloom Filter的高效弱状态路由算法.DWalker基于有向随机网络,采用指数衰落Bloom Filter来发布和传播每个节点共享资源的信息,且其最大传播距离小于网络中任意两点之间距离的期望值,从而有效抑制了衰落Bloom Filter在传播过程中的多径叠加问题.DWalker采用多个Bloom Filter而不是单个Bloom Filter来表达一项路由条目,在单个Bloom Filter的错误发生概率达到设计上限时,可按需动态增加新的Bloom Filter,以将更多资源对象信息纳入到当前路由条目中.DWalker仅根据当前节点的各项路由条目中值为1的比特位所占的最大比例,以及查询消息在正确转发方向对应的路由条目中对应比特位中值为1的个数的临界值,就能使进入目标对象传播范围内的查询消息以较高的概率辨认出正确的路由方向.理论分析和实验结果表明,DWalker能够以较低的查询消息代价、较小的路由条目存储开销以及较短的查询时延,使绝大多数查询消息沿正确方向转发,从而获得较高的查准率.