Quality-of-service control in GRAMS for ATM local area network

摘要

Gopher-style real-time ATM multimedia services (GRAMS) is a multimedia system designed for an ATM local area network with the server providing multimedia services to multiple users in real-time. The major goal of this system is to serve heterogeneous media requests so that every client served has satisfactory service while the network bandwidth and the host capacity are fully exploited. Therefore, a server that can determine the service rates and successfully multiplex media transmissions according to the quality-of-service (QoS) requirement of each request becomes the key component of this system. However, given the heterogeneity of QoS requirements from different types of media, it is usually very difficult to clearly specify and accurately measure the QoS for these media. Also, it is difficult to control the QoS in a distributed-multimedia environment. We propose in this paper a simple yet effective way to measure QoS in the GRAMS system. Based on the GRAMS system architecture, we use different kinds of starvation counters to measure system resource utilization and individual service quality. These counters are employed as major QoS parameters for the admission and rate-control algorithms in the GRAMS server that are under intensive evaluation and refinement. Experimental results are also presented, showing the feasibility of simultaneously providing tens of video and images transfer sessions using low-cost workstation technology. Bottlenecks for the video server are identified.