Quality of service driven packet scheduling disciplines for real-time applications: looking beyond fairness

In this paper we focus on real-time scheduling of `soft' real-time data services such as multimedia data, MPEG video streaming and IP telephony, which can tolerate a small degree of loss or delay. We argue that network operators and service providers should be able to select from a range of Quality of Service objectives, including maximizing the number of customers receiving good service. Further, we argue that scheduling disciplines such as fair queueing are unable to achieve such goals and hence there is a need for alternative approaches. We propose a new scheduling scheme, which we call the Dual Queue discipline. We show that the Dual Queue has the flexibility to satisfy a variety of QoS objectives, ranging from existing notions of fairness through to maximizing the number of customers receiving good service. In addition, even the simplest Dual Queue implementation outperforms Fair Queueing, is scalable in the number of active sessions, and can be made fair, if desired, over moderate to long time scales.