Abstract-The concept of CloudNets, virtual networks connecting cloud resources, has recently attracted much interest from both academic as well as business sides. CloudNets can realize the vision of affordable customized infrastructures. In particular, such networks are expected to be offered even in federated environments with multiple providers. Inter-provider communication about requirements or provisioning of truly customized virtual environments however require a powerful flexible resource description language (RDL). While extensibility and expressiveness seem to be natural requirements for such a language, we identify another less intuitive requirement affecting all actors (or stakeholders) in their economic benefits: the possibility to omit arbitrary specification details and to remain vague while at the same time describing real world scenarios. Not only may a description language ignoring this constraint easily become too bulky to use, it is also likely to force players to focus on details they are not interested in or lack the knowledge to map their actual requirements to. This paper identifies detailed requirements for an RDL to allow for topology and requirement communication in business scenarios. Furthermore, we present the FleRD flexible resource description language for multi-provider virtual network architectures. FleRD is fully incorporated in our own CloudNet prototype architecture.
I. INTRODUCTIONVirtualization has become an important paradigm in the development of today's Internet. Decoupling service applications and virtual components from the constraints of the underlying (substrate) physical infrastructures, it facilitates efficient use of the given resources and eases the provisioning and maintenance of a better service quality. The convergence of node and link virtualization technologies opens many new possibilities. Many research efforts (e.g., in the context of testbed virtualization projects [7], [8]) have been started to build isolated virtual service networks over the same physical infrastructure. In the future, customers will be able to quickly request and use arbitrarily specified CloudNets [6], virtual networks connecting cloud resources. These networks are mapped to (and hosted by) the shared physical substrate resources.In order to surpass the provisioning of simple virtual network topologies and to leverage the potential of truly customized networks, efforts to find flexible ways of describing CloudNets and their properties are underway (e.g., [2], [18]). Properties range from service level over geographical down to embedding constraints (see e.g., [4]) and may possibly even include measurement results. Some of the description languages take ontological approaches in the context of automated reasoning. In contrast, we consider a business scenario in which the language is used for inter-provider communication.