Adaptive Search Radius – Using hop count to reduce P2P traffic

Abstract

Peer-to-Peer (P2P) file sharing accounts for a very significant part of the Internet’s traffic, affecting the performance of other applications and translating into significant peering costs for ISPs. It has been noticed that, just like WWW traffic, P2P file sharing traffic shows locality properties, which are not exploited by current P2P file sharing protocols. We propose a peer selection algorithm, Adaptive Search Radius (ASR), where peers exploit locality by only downloading from those other peers which are nearest (in network hops). ASR ensures swarm robustness by dynamically adapting the distance according to file part availability. ASR aims at reducing the Internet’s P2P file sharing traffic, while decreasing the download times perceived by users, providing them with an incentive to adopt this algorithm. We believe ASR to be the first locality-aware P2P file sharing system that does not require assistance from ISPs or third parties nor modification to the server infrastructure. We support our proposal with extensive simulation studies, using the eDonkey/eMule protocol on SSFNet. These show a 19 to 29% decrease in download time and a 27 to 70% reduction in the traffic carried by tier-1 ISPs. ASR is also compared (favourably) with Biased Neighbour Selection (BNS), and traffic shaping. We conclude that ASR and BNS are complementary solutions which provide the highest performance when combined. We evaluated the impact of P2P file sharing traffic on HTTP traffic, showing the benefits on HTTP performance of reducing P2P traffic. A plan for introducing ASR into eMule clients is also discussed. This will allow a progressive migration to ASR enabled versions of eMule client software. ASR was also successfully used to download from live Internet swarms, providing significant traffic savings while finishing downloads faster.