Analysis of the BitTorrent Protocol Modified with Multicast

Abstract

Peer to Peer (P2P) computer networks rely on direct connections between participants instead of conventional centralized resources. These networks are useful for many purposes, but the killer application nowadays is file sharing. BitTorrent is a very popular protocol for this matter. In this paper, we use a multi-agent model of a BitTorrent network. In it, each BitTorrent client is an agent that interacts with other agents and reacts autonomously, following the same decision algorithms as a real client. Their goals are downloading contents in the shortest possible time and sharing them with other agents. The use of this multi-agent model allows us to introduce modifications to the protocol. We have modified this model to use multicast. A multicast transmission consists in sending information in a network to multiple destinations simultaneously, using a more efficient strategy: to send the message on each link of the network only once and to create copies when the links to the destinations are divided. We have evaluated how BitTorrent performs using multicast and compared to its normal behavior.