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.