Abstract: The present invention allows bandwidth available on a network to be dynamically controlled. In particular, the present invention allows the maximum bandwidth available to an end client to be limited when the network is congested, thereby preserving bandwidth for higher priority data. In addition, the present invention allows even low priority data to be sent with the benefit of the full bandwidth then available on the network when the network is not congested. In addition, the invention may be used to control access to a computer network by known and unknown users.