Special issue on future network: software-defined networking

Computer networks have to support an everincreasing array of applications, ranging from cloud computing in datacenters to Internet access for users. In order to meet the various demands, a large number of network devices running different protocols are designed and deployed in networks. As a result, network management and the deployment of new protocols and applications are quite challenging. On one hand, network operators have to manage so many different network devices and manually configure these devices using different tools. On the other hand, vendors use different physical infrastructures as well as software interfaces to manufacture devices, which makes it difficult for researchers to implement new functions in devices. Therefore, network infrastructure and architecture design face great challenges. Software-defined networking (SDN) has been proposed as a new way to facilitate network evolution. SDN decouples the data and control planes, and removes the control plane from network hardware. In SDN, all the devices are controlled by a centralized controller through open protocols, such as OpenFlow, BGP, and NETCONF. Then, control functions are implemented in the centralized controller to realize operational efficiency and reduce costs. Thus, it dramatically simplifies the network, and brings many potential benefits in terms of network management, network virtualization, trouble shooting, and other new network function deployments. In fact, the advantages of SDN technology are attracting great attention from both academia and industry. However, the current technologies of SDN have some limitations. In the perspective of architecture, the centralized controller needs to control all the resources of the network, and therefore the scalability of centralized control becomes an important problem in SDN. Additionally, compared to the distributed design that makes forwarding decisions locally, centralized control inevitably increases the delay of packet forwarding and thus affects the performance of applications. Therefore, using the distributed control plane and choosing the optimal placement of the controller are important for the performance of the network. In the perspective of network functions, SDN brings agile and programmable controllability, but leveraging this powerful controllability to design new network functions for cloud datacenters, wireless networks, or enterprise networks remains a challenge. Motivated by the above considerations, we bring together researchers, developers, practitioners, and educators to identify and discuss the technical challenges and recent advances related to SDN. This special issue aims to attract the attention of both academia and industry in developing advanced and innovative SDN technologies. This special issue comprises eight best papers selected from the submissions. The topics in this special issue cover both theoretical analyses and practical systems. To survey software-defined wireless networks (SDWNs) and their technologies, Feng et al. (2016) presented the architecture and the possible research directions of SDWN, and then investigated several important technical aspects of SDWN and analyzed how the SDN approach can be incorporated to enhance network performance with these aspects. Frontiers of Information Technology & Electronic Engineering www.zju.edu.cn/jzus; engineering.cae. cn; www.springerlink. com ISSN 2095-9184 (print); ISSN 2095-9230 (online) E-mail: jzus@zju.edu.cn