Bandwidth allocation in peer-to-peer file sharing networks

We present a model of bandwidth allocation in a stylized peer-to-peer file sharing network with s peers (sharers) who share files and download from each other and f peers (freeriders) who download from sharers but do not contribute files. Assuming that upload bandwidth is scarcer than download bandwidth and efficient allocation, we compute the expected bandwidth obtained by each peer. We show that (i) while the exact formula is complex, s/(s + f) is a good approximation and (ii) sharers (freeriders) obtain bandwidth larger (smaller) than s/(s + f). The paper constitutes a first step towards a general analytical foundation for scarce resource allocation in peer-to-peer file sharing networks.