We would like to thank a number of people for their contributions to this project. Neal Cardwell, Geoff Voelker, Alec Wolman, Matt Zekauskas, David Wetherall and Tom Anderson delivered valuable feedback on this paper and on the development of sting. Vern Paxson provided the impetus for this project by suggesting that it would be hard to do. USENIX has graciously provided a student research grant to fund ongoing work in this area. Finally, Tami Roberts was exceptionally generous and accommodating in supporting the author during the paper submission process.