On uncoordinated file distribution with non-altruistic downloaders

We consider a BitTorrent-like file sharing system, where the peers interested in downloading a large file join an overlay network. The seed node possessing the file stays in the system, whereas all other peers are non-altruistic in the sense that they leave the system as soon as they have downloaded the whole file. We consider a flash crowd scenario, where the peers join the overlay simultaneously. We show that the chunk selection algorithm is critical, propose an analytic approach to the process, and find that the encounters can be restricted to neighbours in a Chord overlay without losing much in performance.