The SDN paradigm allows networks to be dynamically reconfigurable by network applications. SDN is also of particular interest for NFV which deals with the virtualization of network functions. The network programmability offered by SDN presents then various advantages but it also induces various threats regarding potential attacks on the network. For instance, there is a critical risk that a hacker takes over the network control by exploiting this SDN network programmability (e.g., using the SDN API or tampering a network application running on the SDN controller). This paper proposes then an approach to deal with this possible lack of trust in the SDN controller or in their applications. This approach consists in not relying on a single controller but on several 'redundant' controllers that may also run in different execution environments. The network configuration requests coming from these controllers are then compared and, if deemed sufficiently consistent and then trustable, they are actually sent to the network. This approach has been implemented in an intermediary layer (based on a network hypervisor) inserted between the network equipments and the controllers. Experimentations have been performed showing the feasibility of the approach and providing some first evaluations of its impact on the network and the services.

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Abstract-The aim of this paper is to introduce and present the main drivers and basic concepts for SLA management. We discuss the business requirements according to two points of view: the Customer and the Service Provider, and we go into more detail on the technical requirements for both the SLA contract itself and the SLA Management system. Finally, we give an overview of SLA management open issues in the industrial and research community.

UML Specifications provides some guides for the description of performance requirements, but these requirements are represented with natural language constraints. This paper introduces UML extensions for the representation of temporal requirements and resource usage and their automatic evaluation. They are defined using standard UML extension techniques. These standard extensions introduce a set of formal constraints, tagged values and stereotypes, which allow the representation of general latency and capacity quality of service requirements. We have included these extensions in a commercial UML CASE tool that provides scheduling analysis services and results. We use scheduling analysis and simulation techniques in the evaluation.

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