This paper presents a Differentiated Services (Diffserv or DS)architecture for multimedia streaming applications. Specifically, wedefine two types of services in the context of Assured Forwarding(AF) per hop behavior (PHB) that are differentiated in terms ofreliability of packet delivery : the Htgh Reliable (HR) service andthe Less Assured (LA) service. We propose a novel node mechanismcalled Selective Pushout with Random Early Detection (SPRED) that iscapable of simultaneously achieving the following four objectives :(1) a core router does not maintain any state information for eachflow (i.e., core-stateless); (2) the packet sequence within each flowis not re-ordered at a node; (3) packets from HR service aredelivered more reliably than packets from LA service at a node duringcongestion, and (4) packets from TCP traffic are dropped randomly toavoid global synchronization during congestion. We show that SPRED isa generalized buffer management algorithm of both tail-dropping andRandom Early Detection (RED), and combines the best features ofpushout (PO), RED and RED with In/Out (RIO) mechanisms. Simulationresults demonstrate that under the same link speed and networktopology, network nodes employing our Diffserv architecture havesubstantial per- formance improvement over the current Best Effort(BE) Internet architecture for multimedia streaming applica- tions.
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