Search is a fundamental service in peer-to-peer (P2P) networks. However, despite numerous research efforts, efficient algorithms for guaranteed location of shared content in unstructured P2P networks are yet to be devised. In this paper, we present a simple but highly effective protocol for object location that gives probabilistic guarantees of finding even rare objects independently of the network topology. The protocol relies on randomized techniques for replication of objects (or their

more »

... nces) and for query propagation. We prove analytically, and demonstrate experimentally, that our scheme provides high probabilistic guarantees of success, while incurring minimal overhead. We quantify the performance of our scheme in terms of network messages, probability of success, and response time. We also evaluate the robustness of our protocol in the presence of node failures (departures). Using simulation, we show that our scheme performs no worse than the best known access-frequency based protocols, without compromising access to rare objects.