The traffic generated by multimedia applications presents a high degree of burstiness that can be hardly described by a static set of traffic parameters. We present a dynamic QoS negotiation scheme applied to a prototype application that provides temporized data transfer. The dynamic and efficient usage of the resources can be reached with the introduction of the renegotiable variable bit rate (RVBR) service, which is based on the renegotiation of the traffic specification. We describe and discuss the RVBR service and how it applies to resource reservation for Internet traffic with RSVP. We propose an architecture design that we evaluate by accomplishing a prototype implementation, whose performance is measured with temporized file transfer using real MPEG2 video traces. The results we obtained indicate that renegotiation is an efficient mechanism to accommodate traffic fluctuations over the burst time-scale and that the RVBR service can be easily implemented in real applications, using available technology.