Many networked multimedia applications are delay-sensitive, and require services with guarantees of resource availability and timeliness. For networks such as those based on Asynchronous Transfer Mode (ATM), these service requirements are speci ed through Quality of Service (QoS) parameters. QoS guarantees are needed at multiple layers in an end-to-end protocol architecture. Delivering end-to-end QoS requires an architecture for resource management at the system end-points (e.g., computer workstation hosts), as well as in the underlying network. We describe a model for an end-point entity called the QoS Broker. The broker orchestrates resources at the end-points, coordinating resource management across layer boundaries. As an intermediary, it hides implementation details from applications and per-layer resource managers. Services such as translation, admission and negotiation are used by the broker to properly congure the system to application needs. Con guration is achieved via QoS negotiation resulting in one or more connections through the communications system. The negotiation involves all components of the communication system needed for the setup. An important property of the broker is its role as an active intermediary which insulates cooperating entities from operational details of other entities. The broker manages communication among the entities to create the desired system con guration. It can be viewed as a software engineering technique for distributed multimedia system architectures. We have implemented an experimental prototype of a QoS Broker on IBM RISC System/6000 hosts connected by an ATM LAN. This prototype was validated using a telerobotics application. This application has very strict timing constraints. It helped us to identify limitations of our system and requirements for system support, and serves as a testbed for our architecture.
In REF , a model for an endpoint entity called QoS Broker is presented.
The QoS Broker
IEEE Multimedia
Computer Science