An approach for performing congestion avoidance in a switching communication system is disclosed. An input port of the switching communication system receives a bandwidth request from a source. The switching communication system includes a bandwidth control processor that examines the bandwidth request, and multiple output ports. The output ports communicate with various destination sites. A congestion avoidance logic within the switching communication system generates multiple clusters based upon a transmission constraint associated with the output ports; each of the clusters corresponds to a portion of the destination sites. The congestion avoidance logic determines a cluster threshold that corresponds to traffic load distribution among the critical clusters. Additionally, the congestion avoidance logic selectively grants the bandwidth request based upon the determined cluster threshold. This congestion avoidance mechanism has applicability to a packet-switched satellite communication system with an on-board switch; the switch has transmission constraints such that the transmitters of the satellite at the output port of the switch cannot simultaneously transmit to downlink cells, which contain station terminals that are within an interfering distance from one another.