We investigate the problem of congestion control for multicast traffic over datagram packet switched networks and present an end-to-end solution to it. The focus of our study is on multimedia collaborative applications. The group members of such applications, typically, span a heterogeneous inter-network, where routers and links may vary widely in their capabilities. Recently, two end-to-end approaches have been introduced for multicast congestion control: hierarchical multicast (a window based approach), and multiple groups (a rate based approach). In this paper, we introduce a new end-to-end technique for multicast congestion control that utilizes multiple groups and is window based. We have conducted an analytical study to evaluate our work, which shows encouraging results compared to other techniques.