Port Capacity Leasing Games at Internet Exchange Points.

Internet Service Providers (ISPs) lease ports at a public switch in an Internet Exchange Point (IXP) to exchange traffic efficiently with other ISPs present at the IXP. The price paid to lease a port depends on the port capacity, which also impacts the Quality of Service (QoS) experienced by the ISP's traffic exchanged through the IXP switch. In this paper, we analyze the leasing of port capacities at an IXP as a non-cooperative game between the ISPs, and analyze the efficiency at equilibrium as compared to the social optimum. We show that when the IXP switch capacity is not changed in response to the port capacities purchased, there is dominant strategy for each ISP that attains a Price of Anarchy (PoA) of at most 2. If the IXP switch capacity is varied to "match" the aggregate port capacity leased by the ISPs, then bad equilibria can exist. However, under certain reasonable assumptions, the PoA is still guaranteed to be within 2. Simulation studies demonstrate the effect of the per-unit leasing price and switch delay functions on the equilibrium performance; in all scenarios simulated, the social cost at equilibrium was found to be very close to the optimum.