Characteristics of assured service and an alternative RIO scheme in differentiated services networks

Assured Service, a service model of Internet Differentiated Services (DiffServ) architecture, is not so well accommodated by the current Internet environment. This is because the Internet's Transmission Control Protocol (TCP) employs an AIMD (Additive Increase and Multiplicative Decrease) mechanism to control congestion. As a result, Assured Service cannot meet the target rate of high-profile flows in the presence of numerous low-profile flows. In this paper, a significant problem related to Assured Service and some of its causes are described with the help of simulation results. Subsequently, several previous approaches to address the problem of Assured Service are assessed. These deal with the sender, the marker, and/or the dropper. A modified RIO (RED with IN and OUT) algorithm called ARIO (Al-ternative RIO) is also proposed as an alternative solution to the problem. The ARIO classifies queue states into a 'greedy state' and a 'fair state' and applies other dropping rules to each state. A simulation model is used to evaluate the proposed mechanism. The simulation results illustrate that the ARIO may offer significant improvements in the end-to-end performance of Assured Service.