Scalable supernode selection in peer-to-peer overlay networks

We define a problem called the supernode selection problem which has emerged across a variety of peer-to-peer applications. Supernode selection involves selection of a subset of the peers to serve a special role. The supernodes must be well-dispersed throughout the peer-to-peer overlay network, and must fulfil additional requirements such as load balance, resource needs, adaptability to churn, and heterogeneity. While similar to dominating set and p-centers problems, the supernode selection problem must meet the additional challenge of operating within a huge, unknown and dynamically changing network. We describe three generic super-node selection protocols we have developed for peer-to-peer environments: a label-based scheme for structured overlay networks, a distributed protocol for coordinate-based overlay networks, and a negotiation protocol for unstructured overlays. We believe an integrated approach to the supernode selection problem can benefit the peer-to-peer community through cross-fertilization of ideas and sharing of protocols.