Dynamic Window-Constrained Scheduling for Real-Time Media Streaming

This paper describes an algorithm for scheduling packets in real-time multimedia data streams. Common to these classes of data streams are service constraints in terms of bandwidth and delay. However, it is typical for real-time multimedia streams to tolerate bounded delay variations and, in some cases, finite losses of packets. We have therefore developed a scheduling algorithm that assumes streams have window-constraints on groups of consecutive packet deadlines. A window-constraint defines the number of packet deadlines that can be missed in a window of deadlines for consecutive packets in a stream. Our algorithm, called Dynamic Window-Constrained Scheduling (DWCS), attempts to guarantee no more than x out of a window of y deadlines are missed for consecutive packets in real-time and multimedia streams. Using DWCS, the delay of service to real-time streams is bounded even when the scheduler is overloaded. Moreover, DWCS is capable of ensuring independent delay bounds on streams, while at the same time guaranteeing minimum bandwidth utilizations over tunable and finite windows of time. We show the conditions under which the total demand for link bandwidth by a set of real-time (i.e., window-constrained) streams can exceed 100% and still ensure all window-constraints are met. In fact, we show how it is possible to guarantee worst-case per-stream bandwidth and delay constraints while utilizing all available link capacity. Finally, we show how best-effort packets can be serviced with fast response time, in the presence of window-constrained traffic

Preserving conformance for GCRA regulated flows

Traffic policing/shaping has been employed at the edge of networks to ensure proper provisioning of network resources and Quality of Service (QoS) guarantees. As shown in this thesis, however, network flows that have been regulated at the network edge based on traffic descriptors, e.g., GCRA, may still become non-conforming in the network core, depending on the packet scheduling algorithm used. Two supplemental schemes to scheduling algorithms are proposed and analyzed in this thesis to ensure conformance for GCRA regulated flows. The first scheme is to add an additional traffic regulator to shape the traffic more aggressively than required constraints before entering the scheduler. The second scheme explicitly computes the eligible departure time for the next packet of each flow in the scheduler. Performance achievable by both schemes, in terms of the percent non-conforming packets and the average delay, are investigated via simulation, when implemented for the First Come First Serve (FCFS) and the Weighted Fair Queuing (WFQ) schedulers

Application of learning algorithms to traffic management in integrated services networks.

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