Optimization and analysis of computer and network system operations for quality of service (QoS) assurance

Various network services, such as webcasting, audio/video conferencing, and file transfer are being deployed over the Internet. This requires computers and network systems to provide the guarantee of the service being provided to the receiver. The requirements of the application are specified in terms of the Quality of Service (QoS) metrics such as delay and response time.;A number of important research questions remain concerning computer and network systems with QoS requirements. The focus of this paper is on the timeliness aspect of QoS. In particular, three problems are considered in this study: (1) Stability problem: minimizing waiting time variance (WTV) on multiple identical parallel service providers; (2) Conformity problem: providing end-to-end delay guarantee for instantaneous jobs over the large complex network system; and, (3) Adaptation problem: establishing quantitative Activity-State-QoS (ASQ) adaptation model for a given service such as voice communication service. Each of the three problems addresses one important aspect of QoS. For the stability problem the NP-completeness is proven with bidirectional polynomial transformations to the completion time variance (CTV) problem. Several optimality properties are presented along with two polynomial time heuristic algorithms.;For the conformity problem two distributed reservation protocols are proposed with their performance compared to the best effort model. It is shown in the simulation results that the two proposed protocols are significantly superior to the best effort model in terms of delay for both small and large network systems. For the adaptation problem significant system counters are identified with proper grouping. Activity, system states, and QoS performance are characterized by a proper set of performance counters, and their performance and iterations are analyzed using ANOVA and Tukey's test.;This research approaches the QoS problems in three different yet fundamental aspects: Conformity, Stability and Adaptation. The results presented in this study have applications to QoS assurance for computer and network systems.