In a video multicast session, the receivers may possess different capabilities or be connected to the network through a variety of different access speeds. Multicasting video traffic at any one rate to all of the receivers can be unfair as some receivers may experience high losses while others find that their full reception capacity is not fully utilized. Layered video multicast protocols have been developed to address this intra-session fairness problem. In such protocols (e.g., RLM and LVMR), video is multicast in multiple layers over separate multicast groups. Receivers join as many layers as they can handle. While protocols such as RLM and LVMR have been shown to successfully address the intra-session fairness issue in video multicast, they do not address the issue of inter-session fairness, i.e., fair sharing between multiple video sessions and TCP sessions. In this paper, we demonstrate and develop insight into the inter-session fairness problem through a set of simulation experiments. We then propose a novel idea to improve inter- session fairness for layered video multicast protocol: layer-based congestion sensitivity mechanism, and finally evaluate it with some other end-to-end schemes designed to promote inter-session fairness when used to augment layered video multicast protocols.
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