Multimediacommunication,with its strong requirementsfor high speed, assured quality, and reliable networking, is stimulating a great research e ort towards the development of real-time protocols. Some protocols of this type have been proposed, which o er communication services with di erent levels of commitment in providing quality of service guarantees. In this paper we study the feasibility of an extended client interface that allows more exibility in the client-network interactions. The proposed model improves the utilization of network resources, and increases the network's capability to support multimedia tra c, while continuing to o er a guaranteed quality of service. Keyword Codes: C.2.0; C.2.1; C.2.2