An accumulation-based, closed-loop scheme for expected minimum rate and weighted rate services
Traditionally QoS capabilities have been constructed out of open-loop building blocks such as packet schedulers and traffic conditioners. In this paper, we consider closed-loop techniques to achieve a range of service differentiation capabilities. We use an accumulation-based congestion control scheme [Y. Xia, D. Harrison, S. Kalyanaraman, K. Ramachandran, A. Venkatesan, An accumulation-based congestion control model, in: IEEE International Conference on Communications, Anchorage, Alaska, May 2003] as a data-plane building block to provide an expected minimum rate service that is similar to ATM ABR, Frame Relay CIR/PIR and DiffServ assured service and a weighted rate service that achieves a significantly larger range than the loss-based approaches that extend TCP [ACM Computer Communication Review 28 (3) (1998); T. Nandagopal et al., Scalable service differentiation using purely end-to-end mechanisms: features and limitations, IPQoS'00, June 2000]. The central theme is to allocate router buffer space among competing flows in a distributed manner to meet the rate differentiation objectives. Be cause both services are provided using congestion control mechanisms, they are meaningful in steady state and can be modelled as moving the equilibrium in Kelly's nonlinear optimization framework [Journal of the Operational Research Society 49 (1998) 237]. This scheme needs no admission control; instead, during oversubscription it degrades to a well-defined, policy-controlled bandwidth allocation. It does not require Active Queue Management (AQM) at bottlenecks with sufficient buffer. However, with AQM, we achieve near zero queue with high utilization at bottlenecks. We use ns-2 simulations and Linux kernel implementation experiments to demonstrate the performance of the services. Some practical issues and open questions are also discussed.
quality of service differentiated services optimization-based congestion control