Understanding Locality-Awareness in Peer-to-Peer Systems

Locality-awareness is one of the essential characteristics for peer-to-peer (P2P) systems. Recently, many locality-aware algorithms have been proposed, in which locality can be defined as different network metrics. In this paper, we compare different performance optimization goals between peer users and ISPs, and then present a detailed simulation study to accurately explore how locality-aware algorithms based on different network metrics influence the performance of real P2P systems. Two widely deployed P2P systems, including BitTorrent, a content-distribution system, and CoolStreaming, a media streaming system, are tested under the real data set from PlanetLab in our extensive simulations. Experimental results suggest that selecting neighbors within the same AS is desirable, which can decrease user experienced delays and keep traffic locality.