Quality of Service - An Overview
Key: SW97-3
Author: Jens Schmitt, Lars Wolf
Date: April 1997
Kind: @techreport
Abstract: In the last few years new types of distributed computer-based applications have appeared which have differing requirements in comparison to previously known applications. The most prominent of these applications types are multimedia applications. These deal with discrete media data (such as text and graphics) and continuous-media data (like audio and video) and request, due to the time-criticality of the audiovisual data, that retrieval, processing, transfer, and presentation of that data takes timing aspects into account. This means that all components involved in such operations must be capable of handling a well-defined quality of service (QoS). The most important QoS parameters are used to request (1) the required capacities of the involved resources, (2) compliance to end-to-end delay and jitter as timing restrictions, and (3) restriction of the loss characteristics. Work on the notion of and mechanisms to provide QoS in general purpose computer systems has started around the late 1980 / early 1990 (mostly, with a few earlier exceptions) within the research community. Since that, interest and research effort has increased much and (partially) moved into development. While the advent of QoS support in products has not been very broad by now, it can be expected that this will change soon because of gained experiences with such technology and also increased public interest in distributed multimedia applications. The purpose of this paper is to give an overview about QoS - the notion, the issues which must be addressed, and approaches for QoS provisioning such as architectures and protocols. We describe aspects which have already been tackled with, as well as recently upcoming aspects which must be addressed in the future. To fulfill its purpose as an overview, the paper considers prominent models from research existing already for some time and currently followed approaches. The most active research area with respect to QoS is perhaps the field of communication systems. QoS is also under study in other areas, e.g., disk scheduling within video-servers. However, due to its importance and the research activity, communication system QoS aspects will be the main focus of this paper.
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