Guaranteeing Statistical QoS to Regulated Traffic: The Single Node Case

Multimedia traffic can typically tolerate some loss but has rigid delay constraints. A natural QoS requirement for a multimedia connection is a prescribed bound on the the fraction of traffic that exceeds an end–to–end delay limit. We propose and analyze a traffic management scheme which guarantees QoS to multimedia traffic while simultaneously allowing for a large connection–carrying capacity. We study our traffic management scheme in the context of a single node. In order for the node to guarantee QoS, each connection’s traffic is regulated. In order to support many connections, the link statistically multiplexes the connections’ traffic. The scheme consists of (i) cascaded leaky–buckets for traffic regulation, (ii) smoothers at the ingresses, and (iii) bufferless statistical multiplexing within the node. For this scheme we show that loss probabilities are minimized with simple one–buffer smoothers which operate at specific minimum rates. We also show that the worst–case input traffic is extremal on–off traffic for all connections. These two results lead to a straightforward scheme for guaranteeing QoS to regulated traffic. Using MPEG video traces, we present numerical results which demonstrate the methodology. Finally, we compare the bufferless scheme with buffered statistical multiplexing. Keywords—Bufferless Multiplexing, Call Admission Control, Multimedia Traffic, Regulated Traffic, Statistical Multiplexing, Statistical QoS, Traffic Smoothing.