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Delay Guaranteed Cross Pushout and Loss Rate Differentiation for DiffServ Networks


In DiffServ IP network, bandwidth and buffer space are allocated for flow aggregates to guarantee the Assured Forwarding (AF) [3] service. It will be ideal, if the input traffic characteristics are known a prior then the resource can be engineered precisely to meet the Quality of Service (QoS) requirements. However, in reality the input traffic is generally unpredictable due to bursty traffic in volume and due to the destinations of traffic flows being dynamic and random. As a result, a static bandwidth and buffer allocation guarantees only the throughput and delay bound, but the loss rate of each flow aggregate varies. We have developed a cross pushout scheme to allow one flow aggregate to "borrow" bandwidth from another flow aggregate by pushout. In this paper we will describe the mechanism and show that if all the packets have the same size in a system like ATM, our Delay Guaranteed Cross Pushout (DGCP) scheme can adjust loss rates among flow aggregates according to the desired loss rate differentiation target without compromising the overall loss rate. We will also demonstrate that the mechanism guarantees that all packets can still meet their respective delay bounds by using the bandwidth in a smarter way.