A Survey of Network QoS Needs of Advanced Internet Applications — Working Document —

During the last few years the Internet has grown tremendously and has penetrated all aspects of everyday life. Starting off as a purely academic research network, the Internet is now extensively used for education, for entertainment, and as a very promising and dynamic marketplace, and is envisioned as evolving into a vehicle of true collaboration and a multi-purpose working environment. Although the Internet is based on a best-effort service model, the simplicity of its packet-switched design and the flexibility of its underlying packet forwarding regime (IP) accommodate millions of users while offering acceptable performance. At the same time, exciting new applications and networked services have emerged, putting greater demands on the network. In order to offer a better-than-best-effort Internet, new service models that offer applications performance guarantees have been proposed. While several of these proposals are in place, and many QoS-enabled networks are operating, there is still a lack of comprehension about the precise requirements new applications have in order to function with high or acceptable levels of quality. Furthermore, what is required is an understanding of how network-level QoS reflects on actual application utility and usability. This document tries to fill this gap by presenting an extensive survey of applications’ QoS needs. It identifies applications that cannot be accommodated by today’s best-effort Internet service model, and reviews the nature of these applications as far as their behaviour with respect to the network is concerned. It presents guidelines and recommendations on what levels of network performance are needed for applications to operate with high quality, or within ranges of acceptable quality. In tandem with this, the document highlights the central role of applications and application developers in getting the expected performance from network services. The document argues that the network cannot guarantee good performance unless it is assisted by well-designed applications that can employ suitable adaptation mechanisms to tailor their behaviour to whatever network conditions or service model is present. The document also reviews tools and experimental procedures that have been recently proposed to quantify how different levels of resource guarantees map to application-level quality. This will allow network engineers, application developers and other interested parties to design, deploy and parameterise networks and applications that offer increased user utility and achieve efficient utilisation of network resources. In its present form, the document is primarily focused on audio and video applications. It presents a detailed analysis of the end-to-end performance requirements of applications like audio-video conferencing, voice over IP, and streaming of high quality audio and video, and gives an overview of the adaptation choices available to these applications so that they can operate within a wider range of network conditions.