Cost-effective broadcast for fully decentralized peer-to-peer networks

Recently, there has been a growing interest in peer-to-peer networks, sparked by the popularity of file sharing applications such as Napster and Gnutella. A typical characteristic of a peer-to-peer system is that all the nodes are equal participants in the network. Gnutella is an example of a ‘pure’ peer-to-peer system, being fully distributed where all nodes are equal and no special nodes with facilitating or administrative roles are required. Due to its fully decentralized nature, Gnutella implements its services like searching and peer discovery via application-level broadcast. For this, messages are routed through Gnutella’s overlay network by means of flooding. The high cost of flooding limits the scalability of fully distributed peer-to-peer systems like Gnutella. To overcome the problem of scalability, we propose Rumor Mongering (also known as Gossip) as a cost-effective alternative to flooding to implement application layer broadcast in decentralized peer-to-peer networks. We introduce a new version of Rumor Mongering, called Deterministic Rumor Mongering, which makes use of the fact that most peer-to-peer network topologies display a power-law distribution in their node degree, to implement a more intelligent routing strategy. Using simulation, we show that Deterministic Rumor Mongering performs broadcast at a significantly lower cost than flooding, at the cost of a slightly reduced reliability and increased time of completion of the