| Abstract | File swarming is a popular method of coordi-nated download by which peers obtain a file from an under-
provisioned server. Critical problems arise within this domain
when users act selfishly, yet most systems are built with altru-
ism assumed. Working under the assumption that all peers
are greedy, we introduce the Fair, Optimal eXchange (FOX)
protocol. FOX, in addition to effective and robust application
of the tit-for-tat incentive mechanism, provides theoretically
optimal download times when everyone cooperates. Under
our assumption of server and peer capabilities, we develop a
strong threat model that provides peers with the incentives to
not deviate from the protocol. From a theoretical perspective,
we prove FOX’s optimality and incentive properties, even
when the network consists only of purely self-interested peers.
We also discuss issues in implementing and deploying such a
system, and address the cost of ensuring fairness in a domain
where efficiency is so important.
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