As more and more organizations move to cloud, it is inevitable that cross-organizational collaboration will need to be supported in the cloud. In this paper, we explore models for collaboration among clouds whose resources are distributed across multiple cloud service providers. In particular, we focus on collaboration and sharing of resources in an infrastructure as a service cloud, where compute resources complemented with storage and networking are offered as a service to customers by cloud service providers. We develop a multi-cloud trust model at different scopes of administration. At cloud level, infrastructure resources can be shared between clouds. At lower administrative scopes, cloud service providers are able to share their resources and service instances among customers within multiple clouds. Finally, we formally specify the administrative aspects of multi-cloud collaboration models we develop. We have implemented a proof of concept prototype based on the administrative model of OpenStack, the  de facto  open-source software for building infrastructure as a service clouds.
['Navid Pustchi', 'Ram Krishnan', 'Ravi S. Sandhu']
Authorization Federation in IaaS Multi Cloud