Today we are faced with a huge variety of multimedia and collaborative applications, networks and end-systems. The resulting heterogeneous environment impose new challenges on transport systems. To meet the requirements of heterogeneous receivers in multi-point communication a communication framework based on a so called Group Mediator is outlined. Group Mediators are located within the network and provide multicast support for CSCW and multimedia applications. QoS filters are discussed as Group Mediator modules. A prototype implementation of the Group Mediator based on RSVP is presented.