A New Approach for Providing Quality-of-service in a Dynamic Network Environment

This paper looks at issues involved in attempting to provide Quality of Service (QoS) support in a dynamic environment. We focus on a resource reservation based approach, which we believe is attractive for military applications, but becomes especially difficult in a dynamic network environment. This is because available resources reserved for a particular flow may contract after they have been "committed" to the flow, causing the reservation to be dropped. Our approach is to expand the semantics of the reservation, so that instead of being a single value indicating the level of service needed by an application, it becomes a range of service levels in which the application can operate, together with the current reserved value within that range. This provides the network flexibility so that reservations can be maintained as network conditions change. Rather than forcing the network to make a binary "admit/fail" decision for each flow, the network provides feedback to applications on the current reservation level. Based on this feedback, applications can adapt their behavior to what the network can support. We have developed a prototype implementation of this concept, running as an extension to the Reservation Setup Protocol (RSVP) protocol. We are currently evaluating the implementation in a testbed network where we can vary link bandwidth. The testbed also includes several adaptive applications (audio, video, data transfer) running over the User Datagram Protocol (UDP). The paper discusses our approach, testbed, experiences to date, and current plans.