A layered and distributed architecture for a training and experimentation cloud (hTEC) is introduced. The technical challenges of hTEC are discussed, and the solutions are explained. The hTEC layered architecture is aligned with the hierarchy and interrelations among the infrastructure, platform and software as a service models. The interfaces between the layers are also specified to complete the architecture. Prototypes for a subset of the hTEC services and interfaces are being implemented in a testbed called BSigma, where the hTEC architecture is evaluated. Preliminary results from our experiments are presented.