Business-Driven Optimization of Policy-Based Management solutions

We consider whether the off-line compilation of a set of Service Level Agreements (SLAs) into low-level management policies can lead to the runtime maximization of the overall business profit for a service provider. Using a simple Web application hosting SLA template for a utility service provider, we derive low-level QoS management policies and validate their consistency. We show how the default first come first served (FCFS) mechanism for the runtime scheduling of triggered policies fails to deliver an all times maximum business profit for the service provider. To achieve a better business profit, first a penalty/reward model that is derived from the SLA Service Level Objectives (SLOs) is used to assign runtime utility tags to triggered policies. Then three policy scheduling algorithms, which are based on the prediction of the future state of the running SLAs, are used to drive the runtime actions of the Policy Decision Point (PDP). The prediction function per see involved the unsolved problem of predicting in realtime the evolution of the transient state of a variant of an M/M/Ct/Ct queue. A simple approximative solution to the latter problem is provided. Finally, using the VS policy simulator tool, comparative simulation results for the business profit generated by each of the proposed policy scheduling algorithms are presented. VS is a novel tool which we have developed to respond to the increasing need of benchmarking SLA and policy-based management solutions.