In the future of corporate IT, companies will rely on highly dynamic distributed IT infrastructures. Federation models are envisioned where a given organisation will be both a Cloud provider during periods when its IT infrastructure is not used at its maximal capacity, and a Cloud customer in periods of peak activity.The main contribution of CONTRAIL will be the development of an integrated approach to virtualization, offering Infrastructure as a Service (IaaS), services for federating IaaS Clouds, and Platform as a Service (PaaS) on top of federated Clouds. This service stack will be part of the CONTRAIL open source system, facilitating industrial up-take of Cloud computing. The main outputs of CONTRAIL are a collection of infrastructure services offering network, computation and storage as a service; services to federate IaaS Clouds; a set of high level services and runtime environments for typical Cloud applications, including efficient map/reduce, scalable service-oriented application hosting, and automatic workflow execution; and a set of applications and use cases from the domains of e-business, e-science, telecommunication and media using and demonstrating the CONTRAIL system.CONTRAIL leverages the open source XtreemOS system, developed in the successful XtreemOS European integrated project and which was designed for large scale dynamic infrastructures. XtreemOS integrates services for data, application, security and community management that can be adapted to provide a unified solution for building private, public and federated Cloud infrastructures. CONTRAIL has core virtualization technology integrated with its high-level services and its Cloud management facilities.This unique approach of covering "the whole Cloud" from the core infrastructure, via federation mechanisms, to management services, enables the construction of transparent, trusted and reliable Cloud platforms with operations governed by service level agreements.