An efficient peer-to-peer file sharing exploiting hierarchy and asymmetry

Many peer-to-peer (P2P) file sharing systems have been proposed to take advantage of high scalability and abundant resources at end-user machines. Previous approaches adopted either simple flooding or routing with complex structures, such as distributed hashing tables (DHT). However, these approaches did not consider the heterogeneous nature of the machines and the hierarchy of networks on the Internet. This paper presents the peer-to-peer asymmetric file sharing system (PASS), a novel approach to P2P file sharing, which accounts for the different capabilities and network locations of the participating machines. Our system selects only a portion of high-capacity machines (supernodes) for routing support, and organizes the network by using location information. We show that our key-coverage based directory replication improves the file search performance to a small constant number of routing hops, regardless of the network size.