Fecha de publicación: 05/06/2008 Fuente: WIPO "swarm" Peer-to-peer file sharing clients share file fragments in the background based on rarity values. When a first peer offers a fragment to a second peer to be shared in the background, the second peer checks the rarity of the fragment and identifies one or more fragments from its swarm that is approximately as rare as the fragment being offered. The second peer then offers the one or more fragments in exchange for the originally offered fragment. The first peer may then offer the one or more fragments to other peers in its swarm to be shared in the background.