Combining Multihoming with Overlay Routing (or, How to Be a Better ISP without Owning a Network)

Multihoming and overlay routing are used, mostly separately, to bypass Internet outages, congested links and long routes. In this paper, we examine a scenario in which multihoming and overlay routing are jointly used. Specifically, we assume that an overlay service provider (OSP) aims to offer its customers the combined benefits of multihoming and overlay routing, in terms of improved performance, availability and reduced cost, through a network of multihomed overlay routers. We focus on the corresponding design problem, i.e., where to place the overlay routers and how to select the upstream ISPs for each router, with the objective to maximize the profit of the OSP. We examine, with realistic network performance and pricing data, whether the OSP can provide a network service that is profitable, better (in terms of round-trip time), and less expensive than the competing native ISPs. Perhaps surprisingly, we find out that the OSP can meet all three objectives at the same time. We also show that the MON design process is crucial. For example, operating more than 10 overlay nodes or routing traffic through the minimum-delay overlay path, rarely leads to profitability in our simulations.