An approach is developed to maximize the bandwidth utilization of a network for continually transmitting sources, such as video sources. We assume that the sources use hierarchical encoding and can adapt their source coding rates in response to requests from the network congestion control algorithm, and we use this adaptability as the controlled input for a proportional control algorithm. We model flows entering or leaving the network as step inputs, and use the algorithm as the basis for admission control, using very little intelligence in the switches. We then present simulation results that demonstrate the algorithm working in a number of scenarios.