Abstract: The peer-to-peer (P2P) paradigm has emerged as a viable alternative to overcome limitations of the client-server model namely, in terms of scalability, fault-tolerance, and even operational costs. This paradigm has gained significant popularity with its successful application in the context of file sharing applications. The success of these applications is illustrated by systems such as Napster, Emule, Gnutella, and recently, Bit Torrent. In order to ensure the scalability of these solutions many P2P services operate on top of unstructured overlay networks, which are logical networks deployed at the application level. Unstructured overlay networks build irregular neighboring acquaintanceships around members of the framework. In spite of the irregular nature for these overlays may be alluring Eventually Tom's perusing large portions P2P services, those coming about toponomy might display sub-optimal characteristics, for instance from the point of view of link latency. This may have a significant impact of the performance of P2P services executed over these overlays. In this paper we propose a query routing approach that accounts for arbitrary overlay topologies, nodes with heterogeneous processing capacity, e.g., reflecting their degree of altruism and heterogeneous class-based likelihoods of query resolution at nodes which may reflect query loads and the manner in which files/resources are distributed across the network. The approach is shown to be stabilizing the query load subject to a grade of service constraint, i.e., a guarantee that queries' routes meet pre-specified class-based bounds on their associated a priori probability of query resolution. Experimental results shows the performance benefits in terms of mean delay and reduced complexity. The query resolution probabilities and traffic loads are also studied.
Keywords: P2P networks, Overlay, Query resolution, Query Forwarding, Priori probability.