Understanding the design tradeoffs for cooperative streaming multicast

Video streaming over the Internet is rapidly increasing in popularity, but the availability and quality of the content is limited by the high bandwidth cost for server-based solutions. Cooperative endsystem multicast (CEM) has emerged as a promising paradigm for content distribution in the Internet, because the bandwidth overhead of disseminating content is shared among the participants of the CEM overlay network. Several CEM systems have been proposed and deployed, but the tradeoffs inherent in the different designs are not well understood. In this work, we provide a common framework in which different CEM design choices can be empirically and systematically evaluated. Our results show that all CEM protocols are inherently limited in certain aspects of their performance. We distill our observations into a novel model that explains the inherent tradeoffs of CEM design choices and provides bounds on the practical performance limits of any future CEM protocol. In particular, the model conjectures that no CEM design can simultaneously achieve all three of low overhead, low lag, and high streaming quality.