Summary

In this section, we have used geographic information to study various aspects of wide-area Internet paths that traverse multiple ISPs. We found that end-to-end Internet paths tend to be more circuitous than intra-ISP paths, presumably because of the peering relationships between ISPs. Furthermore, paths that traverse substantial distances within two or more ISPs tend to be more circuitous than paths that largely traverse only a single ISP. Some of this circuitous routing behavior can be attributed to sub-optimal geographic peering between ISPs. Finally, the findings of our geography-based analysis are consistent with the hypothesis that ISPs generally employ hot-potato routing. The presence of hot-potato routing may also explain for why some major ISPs only account for a relatively small fraction of the end-to-end path.