Improving Search Using a Fault-Tolerant Overlay in Unstructured P2P Systems

Gnutella overlays have evolved to use a two-tier topology. However, we observed that the new topology had only achieved modest improvements in search success rates. Also, the new two-tier topology had not reduced the message routing overhead and bandwidth consumption. In this work, we used local information at each node to construct an overlay, Makalu, that improved search performance and reduced bandwidth consumption. The overlay maximized the expansion from each node´s neighborhood while minimizing the latency to its neighbors. We show that for a 100,000 node system, wild card searches using flooding successfully resolved most queries within four hops for object replications ratios as lows as 0.05% (50 randomly distributed copies) with less than 3% duplicate messages. Using attenuated bloom filters to route messages for exact identifier searches, we show that Makalu resolved most queries with less than ten messages for networks as large as 100,000 nodes. The performance of this search is comparable to that of structured P2P systems. Finally, using data from traffic traces of Gnutella in 2003 and 2006, we demonstrated search success rates that were up to five times more successful and required 75% less bandwidth on a Makalu overlay than on a modern Gnutella overlay.