Peer-to-peer computing and networking, an emerging model of communication and computation, has recently started to gain significant acceptance. This model not only enables clients to take a more active role in the information dissemination process, but also may significantly increase the performance and reliability of the overall system, by eliminating the traditional notion of the "server" which could be a single point of failure, and a potential bottleneck. Although peer-to-peer systems enjoy significant and continually increasing popularity, we still do not have a clear understanding of the magnitude, the traffic patterns, and the potential performance bottlenecks of the recent peer-to-peer networks.

In this paper we study the traffic patterns of Gnutella, a popular large-scale peer-to-peer system, and show that traffic patterns are very bursty even over several time scales. We especially focus on the types of the queries submitted by Gnutella peers, and their associated replies. We show that the queries submitted exhibit significant amounts of locality, that is, queries tend to be frequently and repeatedly submitted. To capitalize on this locality, we propose simple Gnutella caching mechanisms that cache query responses. Using trace-driven simulation we evaluate the effectiveness of Gnutella caching and show that it improves performance by as much as a factor of two.