Abstract-The DiffServ architecture provides a scalable mechanism for QoS introduction in a TCP/IP network. The idea of DiffServ is based on the aggregation of traffic flows at an ingress (or egress) point of a network and the IP packet marking for different priority flows, according to several classification criteria. Two approaches exist in the DiffServ architecture: the absolute and the relative. In absolute DiffServ, an admission control scheme is used to provide QoS guarantees as absolute bounds of specific QoS parameters. The relative DiffServ model provides QoS guarantees per class expressed with reference to guarantees given to the other classes defined. Our study targets at providing relative proportional delay differentiation service based on Class Based Queue (CBQ) scheduler. The main idea is to frequently adjust the service rates allocated to classes of a CBQ scheduler in order to achieve relative delay spacing among classes. The simulation experiments conducted show that our model can attain relative delay, provided that the required Delay Differentiation Parameters (DDPs) are feasible.

SUMMARYSupporting quality of service (QoS) over the Internet is a very important issue and many mechanisms have already been devised or are under way towards achieving this goal. One of the most important approaches is the so-called Differentiated Services (DiffServ) architecture, which provides a scalable mechanism for QoS support in a TCP/IP network. The main concept underlying DiffServ is the aggregation of traffic flows at an ingress (or egress) point of a network and the marking of the IP packets of each traffic flow according to several classification criteria. Diffserv is classified under two taxonomies: the absolute and the relative. In absolute DiffServ architecture, an admission control scheme is utilized to provide QoS as absolute bounds of specific QoS parameters. The relative DiffServ model offers also QoS guarantees per class but in reference to the guarantees given to the other classes defined. In this paper, relative proportional delay differentiation is achieved based on class-based queueing (CBQ) scheduler. Specifically, the service rates allocated to the classes of a CBQ scheduler are frequently adjusted in order to obtain relative delay spacing among them. The model presented can also be exploited in order to meet absolute delay constraints in conjunction with relative delay differentiation provision. Simulation experiments verify that our model can attain relative as well as absolute delay differentiation provided that the preconditions posed are satisfied.

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