In this paper, a control-based bandwidth-on-demand (BoD) scheme for geostationary (GEO) satellite networks is introduced. The proposed scheme, developed for the European Union project "GEOCAST" (Information Society and Technology (IST) programme), deals with the lower priority traffic classes, which have to adapt their transmission rates to the traffic conditions. The novelty of this paper consists of the use of control theory concepts to model the satellite network as a time-delay system and to generate the bandwidth requests. The proposed BoD scheme is stable, adapts its request policy to the current network load and is capable of dealing with congestions. Software simulations have been performed to validate the effectiveness of the proposed scheme.