A Study on Scheduling Disciplines for Providing the Quality of Services Guarantee

本研究计画系针对高速通讯网路连结之多媒体资讯系统，探讨如何借由保留系统资源来保证服务品质的排程原则，并对几种排程原则进行研究与评估。调度规则主要有两种：一种是先来先服务的调度规则，它在不同的逻辑关联之间共享缓冲区。另一种是基于处理器共享方案，在该方案中，通过为不同的关联分配不同的缓冲区来依次服务对象。通过研究，我们发现，不同的协会不同的缓冲区的学科是可行的，以保留资源，从而保证服务质量。通过对虚拟时钟表示法的扩展，提出了这种调度规则的实现方法。公平性准则是调度规则中的一个重要问题，它涉及到如何在应用之间分配资源。其他研究建立的标准都试图在每一个瞬间的应用程序之间提供公平的份额。另一方面，对于像许多真实的应用那样以突发到达的服务请求，需要更灵活的调度规则来提供更高的责任。为此，我们定义了一个更一般的公平性标准，预计将更适合突发服务请求。在这个新准则下，可以产生一类调度规则。我们评估了他们的性能和对各种流量的影响分析，并通过模拟。我们发现它可以预期具有更理想的功能。

This research project is to study on the scheduling disciplines which can guarantee the quality of services by reserving system resources to individual applications in multimedia information systems connected by high speed communication networks.For this purpose, we have studied and evaluated several scheduling disciplines. There are two main kind of scheduling desciplines ; One is the first-come-first-served scheme, which shares buffer among different logic associations. The other is based on the Processor Sharing scheme, in which objects are served in turn by assigning different buffers for different associations. Through our study, we found that disciplines with different buffers for different associations are feasible to reserve resources and hence to guarantee the quality of services. We also proposed the implementation method of such scheduling discipline by extending the Viertual Clock notation.The fairness criterion, which concerns about how to allocate resource among applications, is an important issue when considering scheduling disciplines. Criteria established by other studies are all trying to provide a fair share among applications in every instant of time. On the other hand, with service requests which arrive in bursts like lots of real time applications, there needs a more flexible scheduling discipline to provide higher responsibility. Towards this end, we defined a more general fairness criterion, which is expected to be more suitable for bursty service requests. Under this new criterion, a class of scheduling discipline can be produced. We evaluated their performance and effects on various traffic analytically, and by simulations. We found it can be expected having more desirable features.