Performance Evaluation of Neighborhood Signature Techniques for Peer-to-Peer Search

Peer-to-peer (P2P) systems have received a lot of attention due to the popularity of applications such as SETI, Napster, Gnutella, and Morpheus. The P2P systems present tremendous challenges in searching data items among the numerous host nodes. While search has been studied in a similar but different context, i.e., parallel and distributed database systems, the large scale and dynamic membership change of P2P systems require the search issue to be re-examined. Existing search techniques in unstructured peer-to-peer overlay networks incur excessive network traffic. In this paper, we investigate the issues of trading-off storage space at peers to reduce network overhead in unstructured P2P overlay networks. We propose to use signatures for directing searches, and introduce three schemes, namely complete-neighborhood signature (CN), partial-neighborhood superimposed signature (PN-S), and partial-neighborhood appended signature (PN-A), to facilitate efficient searching of shared content in P2P networks. With little storage overhead, these signatures improve the performance of content search and thus significantly reduce the volume of network traffic. Extensive analysis and simulations are conducted to evaluate the performance of our proposal with existing P2P content search methods, including Gnutella, random walk, and local index. Results show that PN-A gives the best performance at a small storage cost.