1-Bit Schemes for Service Discrimination in the Internet: Analysis and Evaluation
Abstract
Schemes using a single-bit priority field in IP packets have recently been proposed as a low-cost (both in terms of implementation and architectural changes from the current Internet architecture) way to augment the single class best effort service model of the current Internet to include some kind of service discrimination. Such schemes appear attractive, however it is not clear yet what kind of service model they would provide to applications. We examine this in the paper. Specifically, we describe and solve analytic models of two 1-bit schemes recently proposed by Clark and Crowcroft; we obtain expression for performance measures that characterize the service provided to tagged packets, the service provided to non-tagged packets, and the prevalence of denial of service (i.e. the percentage of tagged packets that do not get the better service). We use these expressions, as well as simulations and experiments from actual implementations on a testbed at INRIA, to illustrate the benefits and shortcomings of the schemes. We also discuss implications of our results such as how these schemes can be used to transmit layered data, and how they would interact with tariffing schemes.