Overlay Consolidation of ISP-Provided Preferences

There is growing evidence that mutually beneficial outcomes can be achieved when content distribution overlays and their underlying ISPs collaborate through open interfaces [1]­[8]. For the most part, this collaboration takes the shape of biased overlay topology formation using cost information that each peer obtains from its own local ISP. Although this mechanism is satisfactory if costs are derived from symmetric network properties (e.g. RTT), the consideration of asymmetric costs requires the development of consolidated topology construction algorithms that integrate the information provided by all participating ISPs and use it to produce an overlay topology with desirable global properties. In this paper we propose a generic model for the multi-domain consolidation of ISP preferences expressed as cost-annotatated lists of PIDs (equivalence classes of network peers). Using this model, we propose two consolidated topology construction algorithms: Shared Cost, designed to provide a tradeoff for the interdomain cost asymmetries, and Low Cost, designed to reduce the overall cost that the overlay imposes on all its underlying ISPs. We evaluate these two models through simulation, considering a wide range of ISP and PID size distributions. Finally, we compare the possible gains that these consolidations can provide to the underlying ISPs and the degree to which the consolidated outcomes align with the preferences of each participating ISP.