Design & Performance Study of a Flexible Traffic Shaper for High Speed Networks

Abstract

In networks supporting distributed multimedia, maximizing bandwidth utilization and providing performance guarantees are two incompatible goals. Heterogeneity of the multimedia sources calls for effective congestion control schemes to satisfy the diverse Quality of Service (QoS) requirements of each application. These include admission control at connection set up, traffic control at the source ends and efficient scheduling schemes at the switches. The emphasis in this paper is on traffic control at the source ends. Traffic control schemes have two functional roles. One is traffic enforcement as a supplement to the admission control policy. The other is shaping the input traffic so that it becomes amenable to the scheduling mechanism at the switches for providing the required QoS guarantees. Studies on bursty sources have shown that burstiness promotes statistical multiplexing at the cost of possible congestion. Smoothing the traffic helps in providing guarantees at the cost o f bandwidth utilization. The need for a flexible scheme which can provide a reasonable compromise between the utilization and guarantees is imminent. We present the design and performance study of a flexible traffic shaper which can adjust the burstiness of input traffic to obtain reasonable utilization while maintaining statistical service guarantees. The performance of the traffic shaper for bursty sources is studied using simulation. (Also cross-referenced as UMIACS-TR-95-72)