Balancing pushand pull for data broadcast

The increasing ability to interconnect computexx throughintemet-working, wireless networks, high-bandwidth satellite, and cable networkshas spawned a new class of information-centeredappli-cations based on data dissemination. These applications employ broadcastto deliver data to very large client populations. We have proposed the Broadcast Disks paradigm [Zdon94, Acha95b] for or-ganizing the contents of a data broadcast program and for manag-ing client resources in response to such a program. Our previous work on Bxuadcast Disks focused exclusively on the “push-based” approach, where data is sent out on the broadcast channel accord-ing to a periodic schedule, in anticipation of client requests. In this paper, we study how to augment the push-only model with a “pull-based ” approach of using a backchannel to allow clients to send explicit requests for data to the server. We analyze the scala-bility and performance of a broadcast-based system that integrates push and pull and study the impact of this integration on both the steady state and warm-up performance of clients. Our results show that a client backchannel can provide significant performance im-provement in the broadcast environmen ~ but that unconstrained use of the backchannel can result in scalability problems due to server saturation. We propose and investigate a set of three techniques that can delay the onset of saturation and thus, enhance the performance and scalability of the system