Bilateral and Multilateral Exchanges for Peer-Assisted Content Distribution

17 Pages Posted: 27 Apr 2010

See all articles by Christina Aperjis

Christina Aperjis

Hewlett-Packard Enterprise - Social Computing Lab

Ramesh Johari

Stanford University

Michael J. Freedman

Princeton University - Department of Computer Science

Date Written: February 20, 2010

Abstract

Users of the BitTorrent file-sharing protocol and its variants are incentivized to contribute their upload capacity in a bilateral manner: downloading is possible in return for uploading to the same user. An alternative is to use multilateral exchange to match user demand for content to available supply at other users in the system. We provide a formal comparison of peer-to-peer system designs based on bilateral exchange with those that enable multilateral exchange via a price-based market mechanism to match supply and demand.

First, we compare the two types of exchange in terms of the equilibria that arise. A multilateral equilibrium allocation is Pareto efficient, while we demonstrate that bilateral equilibrium allocations are not Pareto efficient in general. We show that Pareto efficiency represents the “gap” between bilateral and multilateral equilibria: a bilateral equilibrium allocation corresponds to a multilateral equilibrium allocation if and only if it is Pareto efficient. Our proof exploits the fact that Pareto efficiency implies reversibility of an appropriately constructed Markov chain.

Second, we compare the two types of exchange through the expected percentage of users that can trade in a large system, assuming a fixed file popularity distribution. Our theoretical results as well as analysis of a BitTorrent dataset provide quantitative insight into regimes where bilateral exchange may perform quite well even though it does not always give rise to Pareto-efficient equilibrium allocations.

Keywords: Peer-to-peer systems, Markov chains, Economics

Suggested Citation

Aperjis, Christina and Johari, Ramesh and Freedman, Michael J., Bilateral and Multilateral Exchanges for Peer-Assisted Content Distribution (February 20, 2010). Available at SSRN: https://ssrn.com/abstract=1596919 or http://dx.doi.org/10.2139/ssrn.1596919

Christina Aperjis (Contact Author)

Hewlett-Packard Enterprise - Social Computing Lab ( email )

1501 Page Mill Road
Palo Alto, CA 9434
United States

Ramesh Johari

Stanford University ( email )

473 Via Ortega
Stanford, CA 94305-9025
United States

Michael J. Freedman

Princeton University - Department of Computer Science ( email )

35 Olden Street
Princeton, NJ 08540
United States

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