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Receiver heterogeneity severely constrains the performance of multicast congestion control schemes. In the typical TCP-like schemes employed for congestion control in reliable multicast, the performance is dictated by the slowest receiver. Intuitively, in the case where one bottleneck receiver is constraining the performance of other receivers, it would seem that isolating this receiver and carrying out a separate unicast conversation with it will improve the performance of the multicast transmission. In Verma et al. (2002), we formalized this notion of isolation and proposed an algorithm to partition the receivers into disjoint groups based on their bottleneck bandwidth and RTT. The sender then carries out separate conversation with each sub-group formed. In our earlier formulation, an a priori knowledge of multicast tree was assumed and hence topology was not considered while forming groups. However, simulation results have shown that topology indeed plays an important role in the performance of grouping. In this paper, we extend our grouping formulation to include the effects of topology and formulate the problem of joint routing-grouping.