Software-Defined networking (SDN) is a networking paradigm to enable dynamic, flexible, and programmatically efficient configuration of networks to revolutionize network control and management via separation of the control plane and data plane. The SDN technology has evolved in response to the demands from large data centers toward all types of networks, from IoT, enterprise, to ISP networks. On the one hand, SDN has provided solutions for high-demand resources, managing unpredictable data traffic patterns, and rapid network reconfiguration. It is further used to enhance network virtualization and security. On the other hand, SDN is still subject to many traditional network security threats. It also introduces new security vulnerabilities, primarily due to its logically centralized control plane infrastructure and functions. In this paper, we conduct a comprehensive survey on the core functionality of SDN from the perspective of secure communication infrastructure at different scales. A specific focus is put forward to address the challenges in securing SDN-based communications, with efforts taken up to address them. We further categorize the appropriate solutions for specific threats at each layer of SDN infrastructures. Lastly, security implications and future research trends are highlighted to provide insights for future research.INDEX TERMS Software defined networks, OpenFlow, security, threat, attack, vulnerability, network security.• Discussion of the future research directions and open challenges hindering resiliency and security in SDNenabled systems. Different from existing papers, this paper provides an up-to-date discussion about security issues in SDN environments. The presented taxonomy covers security threats ranging from topology discovery, network and app manipulation, flow diversion, teleportation & rootkits, controller placement, access control and authorization, to conventional networking threats. Further, in addition to reviewing existing security solutions and related implications, this paper provides key use cases of SDN technology implementation in smart communication systems. This layout is aimed to enable researchers to focus on the challenges that breach security in SDN communications. Ultimately, this work will provide further insights for future research in the SDN security domain.