In this paper, we propose and evaluate the performance of a continuous media delivery technique, called thresholdbased multicast. Similar to patching, threshold-based multicast allows two clients that request the same video to share a channel without having to delay the earlier request. It ensures sharing by permitting the client with the later arrival time to join an ongoing multicast session initiated for the earlier request. However, threshold-based multicast does not allow a later arriving client to always join an ongoing multicast session. If it has been some time since the ongoing multicast session was started, a new multicast session is initiated. That is, a threshold is used to control the frequency at which new multicast sessions are started. We derive the optimal threshold that minimizes the server bandwidth required. Our analytical result shows that threshold-based multicast significantly reduces the server bandwidth requirement. Furthermore, we perform a simulation study demonstrating the performance gain of continuous media delivery by threshold-based multicast.
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