A model for quality-of-service provision in service oriented architectures

Clients of service-oriented Grids are often concerned with service "quality" and the computational/economic costs for using such a service. A Quality-of-Service (QoS) mechanism should identify the resources needed to execute a service at a specified quality level. It is also important that the selection of such resources is undertaken subject to other constraints, such as increasing/decreasing the costs associated with service execution on a particular set of resources. The QoS models presented here is based on distinguishing between a service provider, a service and a resource. Resources are entities that can be reserved, and a Service-Level-Agreement (SLA) presents a contract that needs to be agreed between a client and a service provider prior to resource allocation. The problem is to determine, given multiple types of QoS requests from clients, the optimal resource allocation to maximize utilization and maintain requested quality levels. A model for such QoS provision is presented, along with a description of optimization heuristics. A QoS system which implements the model, and also involves support for resource reservations in advance is proposed. The implementation extends the functionality of the CoG Core toolkit