Service Routing in Multi-ISP Peer-to-Peer Content Distribution: Local or Remote?
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The popularity of Peer-to-Peer (P2P) file sharing has resulted in large flows between different ISPs, which imposes significant transit fees on the ISPs in whose domains the communicating peers are located. The fundamental tradeoff faced by a peer-swarm is between free, yet delayed content exchange between intra-domain peers, and inter-domain communication of content, which results in transit fees. This dilemma is complex, since peers who possess the content dynamically increase the content capacity of the ISP domain to which they belong. In this paper, we study the decision problem faced by peer swarms as a routing-in-time problem with time-varying capacity. We begin with a system of two swarms, each belonging to a different ISP: One swarm that has excess service capacity (a steady-state swarm) and one that does not (a transient swarm). We propose an asymptotically accurate fluid-approximation for the stochastic system, and explicitly obtain the optimal policy for the transient swarm in the fluid regime. We then consider the more complex case where multiple transient swarms compete for service from a single steady-state swarm. We utilize a proportional-fairness mechanism for allocating capacity between swarms, and study its performance as a non-cooperative game. We characterize the resulting Nash equilibrium, and study its efficiency both analytically and numerically. Our results indicate that while efficiency loss incurs due to selfish decision-making, the actual Price of Anarchy (PoA) remains bounded even for a large number of competing swarms. 2012 ICST Institute for Computer Science, Social Informatics and Telecommunications Engineering.