Control system for a communications network, wherein the control system contains network-control means and information-processing means. Through the quality-control means, a user may set a desired quality (UQS). Additionally, the quality-control means measures quality delivered (UQS') by the information-processing means and compares the two qualities, UQS and UQS'. By reference to a calculated comparison result, parameters are passed on to the network-control means in order to minimize a difference between the desired and delivered qualities. The quality-control means may comprise one or more user agents which may be set through the information-processing means and the communications network.