A shared medium provides a limited amount of bandwidth for communication between nodes. A contention based access protocol is used to access the medium from the nodes. A guaranteed amount of the bandwidth is reserved for quality of service transmission. A controller computes amounts of assigned bandwidth for the nodes so as to track an on-line predicted demand for bandwidth of each node. The amounts of assigned bandwidth are computed so that the sum of the amounts of assigned bandwidth not exceeding a total available amount of bandwidth minus the amount of guaranteed bandwidth reserved for quality of service transmissions. The controller sets regulators in the respective nodes so as to prevent the nodes from attempting to use more than the amounts of assigned bandwidth for the nodes for transmissions other than quality of service transmissions.