XtreemOS

XtreemOS is a European project that 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.

Federated Cloud

XtreemOS has build a Linux-based operating system to support Virtual Organizations for next-generation Grids. As illustrated in the Figure, the individual resources being contributed to the Federated Cloud will be highly heterogeneous in their hardware configuration and system-level organization.
They may take the form of physical machines running the XtreemOS operating system (see panel 1 in the Figure), virtual instances from external Clouds (panel 2), virtual machines running XtreemOS (panel 3), or XtreemOS machines running virtualization software (panel 4).

As Contrail will build on XtreemOS results, you can look at the XtreemOS website for the developments.
More information on http://xtreemos.eu/.