Restructuring peer-to-peer networks

Abstract

The popularity of peer-to-peer networks has grown tremendously in recent times as a result of the ever-improving capabilities of host entities at the edge and the ubiquitous reach of the Internet. The growth has fueled the realization of many peer-to-peer networks in both academia and the commercial arena. Peer-to-peer networks generally fall into one of these categories centralized systems with server-like entities in the network; unstructured systems with random topology and message routing, and structured systems with deterministic topology and routing behavior. Surveying the major peer-to-peer networks in each category, one can conclude that the each of the categories exhibit very different characteristics and properties from one another. This thesis addresses the problems in the peer-to-peer networking space by employing two overarching principles. Firstly, desirable properties of systems in one category can be adopted by another to achieve restructuring. In short, restructuring involves the injection of structure into unstructured networks and conversely loosening the rigidity in structured systems. Secondly, as much as possible, participating peers in the network are designed to be homogeneous in functionality recognizing that they are heterogeneous in capabilities. True to the concept of the peer-to-peer paradigm, this principle keeps participants functioning as fellow peers rather than imposing hierarchical differences in the roles within the network. We describe three contexts in which the issues pertaining to the peer-to-peer networks in view can be addressed by applying the principle of restructuring. For the Mobile Agent Peer-to-Peer architecture, we adopt centralized concepts into the unstructured peer-to-peer network while maintaining homogeneity in functionality through the use of mobile agents. The architecture shields excessive traffic from peers with limited resources and allows more capable peers to share others burden. Through the use of mobile agents, logical hierarchy is avoided and thus the second overarching principle of homogeneity is preserved. For Gnutella Clusters, concepts from the structured systems are adopted to facilitate the formation and maintenance of clustering in unstructured networks. Clustering limits the amount of flooding in the network and thus conserves bandwith. The clustering algorithm is decentralized to all peers, and does not need a set of participants to have special functionality thus preserving the generic nature of all peers. In Autonomic Decentralized Service Directory platform, structure is released from the underlying Chord network to provide better support for service registration and searching. The strict requirements for deterministic routing and lookup which characterize structured systems are granted some leniency for the ability to avoid misbehaving nodes and provide incentives for peers to behave properly.