Geographic Properties of Internet Routing

In this paper, we study the geographic properties of Internet routing. Our work is distinguished from most previous studies of Internet routing in that we consider the geographic path traversed by packets, not just the network path. We examine several geographic properties including the circuitousness of Internet routes, how multiple ISPs along an end-to-end path share the burden of routing packets, and the geographic fault tolerance of ISP networks. We evaluate these properties using extensive network measurements gathered from a geographically diverse set of probe points. Our analysis shows that circuitousness of Internet paths depends on the geographic and network locations of the end-hosts, and tends to be greater when paths traverse multiple ISP. Using geographic information, we quantify the degree to which an ISP's routing policy resembles hot-potato or cold-potato routing. We find evidence of certain tier-1 ISPs exhibiting hot-potato routing. Finally, based on network topology information gathered at CAIDA, we find that many tier-1 ISP networks may have poor tolerance to the failure of a single, critical geographic node, assuming the published topology information is reasonably complete.