Research On Peer Locality In Peer-to-Peer Networks

In P2P systems, every peer not only downloads content from other peers, but also makes use of its upload bandwidth to serve other peers. There is great diversity of different peers both in terms of geographic distance and Internet topology, which introduces tremendous amount of traffic crossing the boundary of Internet Service Providers (ISPs). Such traffic often causes great financial loss to ISPs with active P2P users.By using the accesses of nodes of PlanetLab testbed, a detailed AS-level map including the end-to-end path of all nodes, as well as the relationship of all involved ASes is created. Based on this map, client-server and some P2P solutions with different goals, i.e., minimizing AS hops and maximizing AS revenue, as well as the traditional P2P solution which has no AS-awareness built in are evaluated. The simulation results show the following: (1)P2P solution with the goal of minimizing AS hops can help existing P2P solution to significantly decrease load on Internet, and improve upon the uneven financial distribution among ASes; (2)P2P solution with maximizing AS revenue goal is unnecessary; (3)It is necessary to tradeoff between the goals of achieving fairness among peers and optimizing AS-related performance such as intra-AS traffic and financial fairness.Three practical ways to embed locality-awareness into BitTorrent-like P2P system are proposed, which are tracker locality (neighbor selection), choker locality (choking and unchoking) and picker locality (piece picking). For each policy, closed-form results of average distance traveled by all data pieces and system efficiency are given through analysis based on H-sphere model. The analysis is carried out in two scenarios: downloading which is the mode classic BitTorrent system functions in, and streaming in which BitTorrent is adapted to support the "viewing-while-downloading" feature. These analysis results are confirmed through extensive simulations. Analysis results find the following: (1)When BitTorrent-like system enters steady state, the proposed locality policies can achieve the same system efficiency as the standard BitTorrent system. (2)All proposed locality policies can significantly reduce the network cost. (3)While there is no all-around winner, each policy performs the best at different scenario.BitTube, A web-based peer-assisted video-on-demand system, is intentionally designed to bring minimum disruption to the existing service both in terms of web infrastructure and user viewing experience, and includes a series of novel piece picking policies with built-in locality awareness. By observing peers' downloading behaviors at the piece level detail, server load reductions by different piece picking policies are derived, and the relationship of several design objectives for various piece picking policies are inferred.These policies are also evaluated on PlanetLab testbed by a modified version 3.9.1 BitTorrent source code under BitTube architecture, which support both file downloading and streaming functions and with the three locality policies incorporated. Experiment results not only show that the proposed locality policies can help existing P2P solution to significantly decrease load on Internet and achieve shorter downloading time, but also point out the necessity to tradeoff between the goals of achieving fairness among peers and optimizing AS-related performance such as intra-AS traffic and peer burden fairness.