Network architectures nowadays are not able to address the requirements of future Internet, as they are not sufficient, ossified, and are power hungry on the TCP/IP paradigm. Therefore, to promote the realizable progression toward the new paradigms and modern protocols, modern routers are required to become programmable for the flexible control and dynamic management of both power states and traffic flows. In this scenario, Software Defined Networking (SDN) is considered as an exemplary approach for providing the support of dynamic traffic flows of each node on a network. Besides the benefits that SDN brought to the networking area, there are still crucial challenges such as to design an effective, lightweight API, rich algorithms, and traffic forwarding rules for SDN layers along with the adoption of an energy efficient infrastructure that could have the least effect on the environment. The aim of this research is to drive the attention toward environment friendly adoption and implementation of SDN that could deal with the growing number of users and network equipment. For this purpose, in this research, a comprehensive review on SDN while mapping the characteristics of green computing with SDN is provided. In addition to that, the research stressed on the benefits of Green SDN through a proposed G-SDN framework. Some well-defined case studies are presented to highlight the need of greening an SDN infrastructure. Finally, various research directions are presented to the wide adoption of SDN technology for academia and industry alike. KEYWORDS green computing, green SDN, SDN, software defined networks 1 INTRODUCTION Software Defined Networking (SDN) offers a high level of flexibility, controllability, and programmability in networks with the power of centralized control. The centralized controller at SDN faces a significant performance drawback when dealing with huge network flows. 1 On the other hand, features provided by SDN allows an ease in deploying the strategies that are designed to overcome the existing problems of power and energy-waste. 2 Green computing refers to the reduction of hazard and toxic materials, improved efficiency of energy including recycling of factory wastage, 3 and it has become an integral part to enhance the reliability of each emerging computing domains. Even the cloud and green computing are applicable side by side to make greener internet and enhance services. The former techniques allow the services with ease when required at a cost of complex infrastructure. However, the later approach has edge in providing all of these services with efficient energy usage, recyclability, low environmental impact, reduced carbon emission, and much more facilities. 4 In addition, to provide the promising services to the intended users, wired and wireless networks 5,6 have been followed by many directions in prior studies 5-7 such as the closing of forward and feedback loops. 8 In this way, there exists a variety of designs such as low-power solutions with slow and fast dynamics. Solutions with sl...
