Special issue on Software‐Defined Networking and Network Functions Virtualization for flexible network management

Economical and operational aspects motivate the demand for fundamental changes towards more flexible network management solutions. This trend is stimulated by network virtualization and Software-Defined Networks (SDNs) that emerged in recent years. These technologies allow networks to be operated and managed in a more flexible and cost-efficient manner. As an emerging topic, Network Functions Virtualization (NFV) allows even further flexibility by virtualizing network functions, for example, Dynamic Host Configuration Protocol, Point to Point Protocol over Ethernet, Firewalls or Deep Packet Inspection from dedicated hardware to software components running on commodity hardware. Virtualized network functions are appealing to network operators because they can be migrated and flexibly adapted to current demands. To this end, the goal of this special issue of the International Journal on Network Management (IJNM) on ‘SDN/NFV for Flexible Network Management’ is to address the newly achieved flexibility in network management, particularly for NFV, which opens a set of currently unresolved key questions concerning (i) techno-economic aspects, (ii) security (iii), reliability and (iv) performance. The following key questions are currently very relevant: How to operate virtualized network functions in a reliable manner by providing redundancy and load balancing? Can virtualized network functions provide performance guarantees required for network operations, and how can such virtualized services be benchmarked and compared? Where should network functions be placed to optimize the network subject to different design criteria? How can services be efficiently orchestrated? How can network monitoring in such flexible networks be used to dynamically manage them? A total of 22 submissions were received for this special issue, for which we wish to thank all authors. After extensive review and discussion, four papers were finally selected for publication. The authors of these papers were given the time to update their paper and take thoroughly the review comments and suggestions into account. The selected four papers fall into two areas that play an important role in future programmable networks: (i) network security and (ii) techno-economic analysis of a SDN/NFV-based architectures. In the first area on network security, Röpke et al. (On Network Operating System Security) present an approach to securing the network operating system or SDN controller from malicious third-party applications with the use of sandboxing and access control policies. They motivate the need for their work by presenting selected experiments that show the potential impact that malicious programs could have on a number of contemporary OpenFlow controllers. Experimental results are shown that indicate the authors’ solution is effective at mitigating the demonstrated threats and has minimal impact on performance. This paper is complemented by the work of Basile et al. (Inter-function Anomaly