Achieving high utilization in guaranteed services networks using early-deadline-first scheduling

Among packet scheduling disciplines for providing end-to-end quality-of-service (QoS) guarantees to different applications, two classes of algorithms have received particular attention: those based on generalized processor sharing (GPS) and those based on earliest-deadline first (EDF) scheduling. The powerful properties of GPS-based schemes translate easily into simple call admission control (CAC) procedures. The intense research on GPS has also resulted in very efficient implementation techniques, which have made the cost of these schedulers very affordable. The EDF discipline, in conjunction with per-node traffic shaping [which we refer to as rate-controlled EDF (RC-EDF)] has also been proposed for end-to-end QoS provisioning. However, an appropriate framework for CAC with RC-EDF has not been developed, nor the possible advantages of using RC-EDF in place of GPS have been properly characterized. Furthermore, the implementation complexity of an RC-EDF server is potentially very high, and no technique to reduce costs has been proposed. In this paper, we first formulate an end-to-end CAC framework for RC-EDF that can be implemented in practice. Then, using this framework, we numerically compare the schedulable regions of RC-EDF and GPS and show that, when the traffic mix in the network consists of connections with both stringent and loose delay requirements, RC-EDF can substantially outperform GPS in the number of admitted connections, and can thus achieve much higher network utilization. Finally, we propose a technique to substantially reduce the implementation complexity of a RC-EDF server.