Reference Architecture for StratusLab Toolkit 2.0

The document describes the updated Reference Architecture for StratusLab v2.0, building on D4.1, which described the architecture for StratusLab v1.0. This document contains two main parts, the overall architecture identifying the required services and components of which it is composed, followed by detailed descriptions for each of these elements. For v2.0, the architecture is rationalized and consolidated. For example, the policy validation, caching and cloud storage are integrated as default features. The Appliance Repository is replaced by the cloud storage service. Several services are also added, such as cloud storage, virtual network provisioning and inter-cloud connectivity. From v1.0 to v2.0, incremental versions of the StratusLab distribution will be built and released to provide an increasing amount of the functionality identified in this document, alongside further improvements to the robustness of the distribution.