Multicast applications can involve a large number of receivers with heterogeneous data reception capabilities. In a traditional single-rate multicast session, the transmission rate at the source is chosen to match the lowest capacity path to a receiver in the session. This can cause an under-utilization of higher capacity paths to other receivers. We have previously defined an inter-receiver fairness measure in order to quantify the effect of this underutilization. We also developed protocols that use this measure to guide the choice of the source rate for a single-rate session. In this paper we design and develop a multi-rate protocol in the context of an ATM ABR service to achieve better inter-receiver fairness for a multicast session. The multi-rate protocol we investigate is based on the use of destination set grouping (DSG) where the set of receivers in a multicast session is partitioned into disjoint subgroups. The transmitter carries a separate conversation with each subgroup. Based on a number of grouping heuristics, the DSG protocol attempts to find the partitioning of the receivers that maximizes the inter-receiver fairness of the session. The DSG protocol can result in a session receiving a higher bandwidth allocation when it is split into multiple connections. We address this issue by proposing a mechanism in which the connections split from a single multicast session are treated as a single aggregated-allocation connection (AAC). A set of examples demonstrate the effectiveness of the DSG scheme incorporating the AAC technique on improving inter-receiver fairness for multicast ABR sessions.
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