Today's trend toward network virtualization and software-defined networking enables flexible new distributed systems where resources can be dynamically allocated and migrated to locations where they are most useful. This paper proposes a competitive analysis approach to design and reason about online algorithms that find a good tradeoff between the benefits and costs of a migratable service. A competitive online algorithm provides worst-case performance guarantees under any demand dynamics, and without any information or statistical assumptions on the demand in the future. This is attractive especially in scenarios where the demand is hard to predict and can be subject to unexpected events. As a case study, we describe a service (e.g., an SAP server or a gaming application) that uses network virtualization to improve the quality of service (QoS) experienced by thin client applications running on mobile devices. By decoupling the service from the underlying resource infrastructure, it can be migrated closer to the current client locations while taking into account migration costs. We identify the major cost factors in such a system and formalize the wide-area service migration problem. Our main contributions are a randomized and a deterministic online algorithm that achieve a competitive ratio of O(logn) in a simplified scenario, where n is the size of the substrate network. This is almost optimal. We complement our worst-case analysis with simulations in different specific scenarios and also sketch a migration demonstrator.

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 remainvaguewhile 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.