DHT协议设计选项与抖动问题关联分析

因节点加入和离开引起的抖动是增加结构化P2P网络路由表更新代价的主要原因。为了找出影响网络抖动的关键因素,分析了影响抖动的路由方式、邻居选择、节点加入和节点离开以及并行查找等策略因素,发现任意两种DHT网络分别采用的五种策略都至少有两种不同,对两种DHT网络直接进行比较就很难确定哪些策略能更有效地降低抖动。因此,提出在同一网络内用不同的单个策略对网络抖动进行比较和分析的方法,称之为CSP。通过对现有DHT算法进行改进,使用CSP方法对不同的单个策略进行比较,得出以下结论:迭代路由、快速加入和周期性恢复策略和有效的邻居选择算法能更有效地降低网络的抖动。

The Effect of the DHT Design on the Maintenance Cost Induced by Churn

In the structured peer to peer network,the churn caused by nodes’ joining and leaving frequently increases the cost of updating the routing table. With the problem of churn,which is difficult to handle by DHT,the concept of inverse neighbor nodes is proposed. This  means the node is in their routing tables. The number of inverse neighbor nodes for six DHT networks is computed. We find that the most significant factors affecting churn are routing, neighboring nodes selection, bootstrapping and the recovery policy,and the parallel lookup. In any two existing DHTs, there are at least two different policies in the five policies . Therefore, the method that compares the routing tables update costs of two structured p2p network directly cannot decide which policy can deal with churn better, so we propose a new method of analysis: CSP. By improving the existing DHTs,we compare each different policies by CSP. The experimental results suggest that iterative routing, fast bootstrapping, periodic recovery,and the effective neighboring nodes selection algorithm can decrease the cost of updating the routing tables in high churn.