Cross-layer SLA Selection for Cloud Services

Cloud computing is a paradigm for enabling remote, on-demand access to a set of configurable computing resources as a service. The pay-per-use model enables service providers to offer their services to customers in different Quality-of-Service (QoS) levels. These QoS parameters are used to compose some bipartisan Service Level Agreement (SLA) between a service provider and a service consumer. A main challenge for a service provider is to manage SLAs for its service consumers, i.e. automatically determine the appropriate resources required from the lower layer in order to respect the QoS requirements of his consumers. This paper proposes an optimization framework driven by consumer preferences to address the SLA dependencies problem across the different cloud layers as well as the need of flexibility and dynamicity required by the domain of Cloud computing. Our approach aims to select the optimal vertical business process designed by cross-layer cloud services, enforcing SLA dependencies between layers. Based on Constraint Programming (CP), our approach can take into account dynamic QoS parameters in a flexible manner to compose the best vertical business process. Experimental results demonstrate the flexibility and effectiveness of our approach.