We thank the members of our research group for their insightful comments. We would also like to thank our shepherd Phil Levis and the anonymous reviewers for their excellent feedback and comments, all of which helped to greatly improve this paper.
This work is supported by the National Science Foundation under the following grants: CCF-0621487, CNS-0509474, CCR-0133456, as well as by generous donations from Network Appliance and Sun Microsystems.
Any opinions, findings, and conclusions or recommendations expressed
in this material are those of the authors and do not necessarily
reflect the views of NSF or other institutions.