Improving Peer to Peer Search With Multi-Tier Capability-Aware Overlay Topologies

The P2P model has many potential advantages (e.g., large scale, fault-tolerance, low cost of administration and maintenance) due to the design flexibility of overlay networks and the decentralized management of cooperative sharing of information and resources. However, the mismatch between the randomly constructed overlay network topology (combined with its broadcaststyle message forwarding infrastructure) and the underlying packet routing introduces difficult performance problems, exemplified by the Short-Cut Effect. This paper presents two peer-to-peer (P2P) system-level facilities to address the problems. First, we propose a capability-aware mechanism to structure the overlay topology in the form of layers that takes peer heterogeneity into account. Second, we develop a Probabilistic Broadening search technique, empowered with capability-sensitive query forwarding scheme which integrates gracefully with result caching techniques to improve the search performance of a P2P system. We believe that efforts on bridging the gap (mismatch) between overlay networks and underlying Internet will bring P2P services beyond pure “best effort” and closer to serious applications with quality of service requirements.