The EGI Federated Cloud integrates community, private and/or public clouds into a scalable computing platform for data and/or compute-driven applications and services. The original architecture was put into production in May 2014. The EGI community has refined the initial concept and evolved its architecture according to emerging user demands.

The architecture is based on the concept of an abstract Cloud Management Framework (CMF) that supports a set of cloud interfaces to communities.

Each resource centre of the infrastructure operates an instance of this CMF according to its own technology preferences and integrates it with the federation by interacting with EGI core components:

• Service registry for configuration management of federated cloud services.
• EGI AAI for authentication and authorisation across the whole cloud federation.
• Accounting for collecting, and displaying usage information.
• Information discovery about capabilities and services available in the federation.
• Virtual Machine image catalogue and distribution, replicating VM images as needed by the user communities in a secure way.
• Monitoring, performing service availability monitoring and reporting of the distributed cloud service end-points.

This integration is performed by using public interfaces of the supported CMFs, thus minimising the impact on site operations. Providers are organised into the Open Standards and OpenStack realms, each realm exposing a homogeneous interface.
The realms use different inter-faces to offer IaaS capabilities to the users: the Open Standards Realm uses OCCI standard (supported by providers with OpenNebula, OpenStack or Synnefo Cloud Management Frameworks), while the Open Stack Realm uses OpenStack native APIs (support limited to OpenStack providers). Open Stack was introduced in the federation in November 2015 and can co-exist with the Open Standards Realm within the same resource provider.

Users can interact with cloud providers in several ways:

• Directly using the IaaS APIs of the resource centres to manage individual resources.
• Leveraging federated IaaS pro-visioning tools that allow managing and combining resources from different providers and enable the portability of application deployments between them. The EGI Federated Cloud task force is currently in the process of evaluating and selecting the best tools for this task.
• Using the AppDB VMOps dashboard, a web-based GUI that simplifies the management of VMs on any provider of the EGI infrastructure. AppDB VMOps relies on the Infrastructure Manager, a Federated IaaS Provisioning tool developed within INDIGO-DataCloud.

Community Platforms are built on top of the federation, either by using IaaS APIs or Federated IaaS provisioning, and provide community-specific data, tools and applications which can be supported by one or more realms. New realms can be defined by agreeing with the providers on which interfaces and EGI core services to use for the federation.