Controller design and closed-loop stability analysis for admission control in Web service systems

IT systems have to provide to their users prescribed Quality of Service (QoS) levels, usually defined in terms of application performance, which must hold irrespectively of the significantly timevarying workload. To handle system overload issues, admission control is used as an overload protection mechanism which rejects requests under peak workload conditions in order to provide QoS guarantees to the running applications. For ensuring QoS levels at design time, the performance of such mechanisms should be a priori guaranteed. To this end, this paper proposes an appropriate controller, the closed-loop stability properties pf which are formally assessed.