ABE: Providing a low-delay service within best effort

We propose alternative best effort (ABE), a novel service for IP networks, which relies on the idea of providing low delay at the expense of maybe les s throughput. The objective is to retain the simplicity of the original Int ernet single-class best-effort service while providing low delay to interac tive adaptive applications. With ABE, every best effort packet is marked as either green or blue. Green packets are guaranteed a low bounded delay in every router. In exchange, green packets are more likely to be dropped (or marked using congestion notification) during periods of congestion than blu e packets. For every packet, the choice of color is made by the application based on the nature of its traffic and on global traffic conditions. Typic ally, an interactive application with real-time deadlines, such as audio, w ill mark most of its packets as green, as long as the network conditions of fer large enough throughput. In contrast, an application that transfers bin ary data such as bulk data transfer will seek to minimize overall transfer time and send blue traffic. We propose router requirements that aim at enfo rcing benefits for all types of traffic, namely that green traffic achieves low delay and blue traffic receives at least as much throughput as it woul d in a flat (legacy) best effort network. ABE is different From differentia ted or integrated services in that neither packet color can be said to rece ive better treatment; thus, flat rate pricing may be maintained, and there is no need for reservations or profiles. In this article we define the ABE service, its requirements, properties, and usage. We discuss the implicatio ns of replacing the existing IP best effort service by the ABE service. We propose and analyze an implementation based on a new scheduling method call ed duplicate scheduling with deadlines. It supports any mixture of TCP, TCP -friendly, and non-TCP-friendly traffic.