SCUBA was inspired by Jacobson's ``video silence suppression'' concept, which uses receiver interest to enable and disable video sources [10]. We are grateful to Hari Balakrishnan and Venkat Padmanabhan for providing constructive comments and lively discussions throughout the writing of this paper. Anindo Banerjea and Tom Henderson provided helpful comments on and corrected oversights in the paper. We thank Deana McCanne for suggesting several improvements to the paper's presentation. A host of people provided constructive criticism on our work when it was first presented at the UCB Daedalus retreat; in particular, we thank Jim Gemmel, Kevin Mills, Srini Seshan, Mark Handley, and Lixia Zhang for their helpful comments. Finally, the anonymous reviewers provided valuable feedback on our work and its presentation.