Improving BitTorrent Traffic Performance by Exploiting Geographic Locality

Current implementations of BitTorrent-like P2P applications ignore the underlying Internet topology hence incur a large amount of traffic both inside an Internet service provider (ISP)´ national backbone networks and over cross-ISP Internet working links. These traffics not only occupy costly bandwidth, but also increase user perceived response latency. ISP-biased neighbor selection proposes to exploit peers´ topological locality by biased neighbor selection, in which a peer chooses the majority of its neighbors from peers within the same ISP. In this paper, we propose to further exploit peers´ geographic locality. First we improved ISP-biased neighbor selection (ISP-Biased+) to take into consideration network locality (or, city locations) within the same ISP. When required neighbor number is relatively much less than seeds available, ISP-biased neighbor selection+ performs much better than original approach, proved by simulations. Next, we propose that a peer could also choose its neighbors from peers of different ISPs within the same city with priority: assist by a well-know Chinese operator´s unique ISP-internetworking content distribution network (CDN), these local cross-ISP traffics can be routed through local CDN cite. Using simulations, we show that cross-ISP traffic burden can be completely shifted to CDN local links and backbone traffic. At the same time, user perceived delay can be significantly reduced.