Interactive multimedia and sensor-based real-time applications on the Internet must be delivered to the receiver at the sender's transmission rate and have bounded end-to-end delay requirements. We call such flows real-rate flows. The resource requirements of such flows can not be met in many environments. Researchers have proposed selectively dropping data in the flow so that the data rate matches available resource capacity (i.e., QoS aabptive, real-rate flows). Application-level QoS adaptation is not well integrated with network scheduling mechanisms and resource management, resulting in slow and inaccurate QoS adaptation, poor flow quality, and unpredictable interactions between adaptive mechanisms. Our proposed resource management service integrates QoS adaptation and networWCpU scheduling mechanisms to offer support for QoS adaptive, real-rate flows. Its goal is to deliver the highest quality flow to the receiver within a bounded delay at the sender's real rate. This service combines two techniques -both based on feedbackreal-rate scheduling and QoS adaptation. Real-rate scheduling uses packet time-stamps to schedule flows along the flow path at the sender's real rate. QoS adaptation drops data at a node when the node's resources are limited, in application-specified priorify order. System modeling issues are discussed and a controller structure is proposed. 1 Overview, Modeling Issues, and System Architecture The advent of high-speed networks and processors has led to a shift fiom desktop computing to a "networkeddevice" computing environment, where desktop computers are inter-networked with real-time devices such as sensors, cameras and displays. These devices stream data that must be delivered and processed in realtime with bounded end-to-end delay. To achieve this goal, network nodes (such as routers) may manage the flow delay by dynamically adjusting the flow rate. These nodes may also automatically adapt flow quality when resources are fully utilized. A feedback-based resource management approach is well suited for performing these functions. The resources allocated to the flow at each stage of the pipeline are regulated using a feedback mechanism, based on local measurements. Since both length and configuration of pipelines change dynamically, it is desirable to create local resource managers (controllers) along the pipeline that can be cascaded safely. (Figure 2) 3613' A means of measurbg, locally, how far ahead or behind a flow is &om achieving the sender's real rate, is necessary to achieve control. One means of measuring this can be achieved by marking packets with time stamps, with the delivery time offset &om first packet in flow. (Figure 3 ) This information allows the resource manager locally to track the flow's rate and determine how it differs fiom its rate bound The resource manager can adjust resources
Goel et al. REF proposed a resource management service to integrate QoS adaptation and network/CPU scheduling mechanisms.
Using feedback control for a network and CPU resource management application
Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148)
Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148)
Computer Science