A Combined Scheduling Scheme for Absolute and Relative Differentiated Services

N. Shenoy (USA) and S. Patchararungruang (Australia)


Quality of Service, scheduling scheme,absloute and relative Diffserv.


Differentiated services (DiffServ) are becoming a ver y popular implementation to provide Quality of Service (QoS) to various Internet applications. Absolute and Relative DiffServ are two recommended approaches to provide QoS in Diffserv. Relative DiffServ is more controllable and less complex and has simple scheduling algorithms, which can be applied to all classes. Absolute DiffServ is complex to implement but can guarantee certain hard QoS which is necessary for some applications. In this paper, we propose a novel scheduling scheme, which has two prime features. Firstly, a single scheduling scheme to support a single Absolute and several Relative differentiated classes. Secondly, it can automatically adjust the "Relative Service Differentiation Ratio" for the Relative Diffserv services based on amount of traffic influx. The second feature called "dynamic differentiation" can be switched off when not required. The proposed scheme can be used with any existing Relative Diffserv scheduling algorithms with a few extra lines of code. We present the performance of this scheme by incorporating it in a Weighted Time Priority (WTP) and a Weighted Fair Queuing (WFQ) scheme and show that irrespective of the algorithm, this scheme is able to provide hard guarantees to the absolute class and maintain relative "dynamic service differentiation" among the other classes. We also provide proof of its successful implementation in the interior routers. Simulations and results are presented and compared.

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