A Trust Model for Competitive Cloud Federations

This paper proposes a trust model for a competitive federation of Cloud computing systems. The reference scenario is a large-scale environment in which different Cloud providers compete in offering their pay-per-use XaaS (Anything as a Service) resources to the various users. In this context, to obtain the assignment of a user request, providers may state to possess more resources than the amount really available: the result could be the provisioning of a services with a lower QoS than expected. A trust model is thus mandatory to help the requester to properly choose the adequate provider on the basis of (i) the reliability shown in the past in providing services, and (ii) the reputation the provider has to other users. In this sense, the paper presents an extension to the RRAF model, which has been suitably adapted to a large-scale environment by means of the introduction of a multi-dimensional approach which fits the various reliability issues, typical of Cloud computing systems.