How to Measure Network Flexibility? A Proposal for Evaluating Softwarized Networks

The emerging trend to softwarize networks based on concepts such as Network Virtualization, Software Defined Networking and Network Functions Virtualization promises to increase flexibility in networking. So far, flexibility is used rather as a qualitative argument for a network design choice. Furthermore, the meaning of flexibility behind such qualitative arguments is highly varying in the state of the art as a common understanding of flexibility is missing. In this article, we present an approach toward evaluating network flexibility through a definition of a flexibility measure, which provides a quantitative analysis and a comparison of different network designs. For us, network flexibility refers to the ability to support new requests that can be, for example, changes in the requirements or new traffic distributions. We show with two case studies, how an application of such measure could lead to a better understanding of different network designs with respect to flexibility. We also illustrate the trade-off between flexibility and cost needed to provide flexibility. With our proposed flexibility measure, we would like to stimulate the discussion toward a more quantitative analysis of softwarized networks and beyond.