Scalable P2P search

Although the traditional client-server model first established the Web's backbone, it tends to underuse the Internet's bandwidth and intensify the burden that dedicated servers face as their load increases.' Peer-to-peer computing relies on individual computers' computing power and storage capacity to better utilize bandwidth and distribute this load in a self-organizing manner. In P2P, nodes (or peers) act as both clients and servers, form an application-level network, and route messages (such as requests to locate a resource). The design of these routing protocols is of paramount importance to a P2P application's efficiency: naive approaches - such as Gnutella's flood routing, for example - can add traffic. P2P systems that exhibit the "small world" property - in which most peers have few links to other peers, but a few of them have many - are robust to random attacks, but can be highly vulnerable to targeted ones. P2P computing also has the potential to enhance reliability and fault tolerance because it doesn't rely on dedicated servers.' Each peer maintains a local directory with entries to the resources it manages. It can also cache other peers' directory entries. Important applications of P2P technologies include distributed directory systems, new e-commerce models, and Web service discovery, all of which require efficient resource-location mechanisms.