Cloud computing market is in rapid expansion due to the opportunities to dynamically allocate a large amount of resources when needed and to pay only for their effective usage. However, many chal- lenges, in terms of interoperability, performance guarantee, and depend- ability, should still be addressed to make cloud computing the right solu- tion for companies. In this chapter we first discuss these challenges and then we present three components developed in the framework of the Contrail project: Contrail federation; SLA manager; and Virtual Execu- tion Platform (VEP). These components provide solutions to guarantee interoperability in a cloud federation and to deploy distributed appli- cations over a federation of heterogeneous cloud providers. The key to success of our solutions is the possibility to negotiate performance and security guarantees for an application and then map them on the physical resources.