With the dynamic demands and stringent requirements of various applications, networks need to be high-performance, scalable, and adaptive to changes. Researchers and industries view network softwarization as the best enabler for the evolution of networking to tackle current and prospective challenges. Network softwarization must provide programmability and flexibility to network infrastructures and allow agile management, along with higher control for operators. While satisfying the demands and requirements of network services, energy cannot be overlooked, considering the effects on the sustainability of the environment and business. This paper discusses energy efficiency in modern and future networks with three network softwarization technologies: SDN, NFV, and NS, introduced in an energy-oriented context. With that framework in mind, we review the literature based on network scenarios, control/MANO layers, and energy-efficiency strategies. Following that, we compare the references regarding approach, evaluation method, criterion, and metric attributes to demonstrate the state-of-the-art. Last, we analyze the classified literature, summarize lessons learned, and present ten essential concerns to open discussions about future research opportunities on energy-efficient softwarized networks.

翻译：随着各类应用的动态需求与严格约束，网络需要具备高性能、可扩展性及适应性。研究人员与产业界将网络软件化视为推动网络演进以应对当前及未来挑战的最佳技术路径。网络软件化必须为基础设施提供可编程性与灵活性，实现敏捷管理，同时赋予运营商更强的控制能力。在满足网络服务需求与约束的同时，考虑到环境可持续性与商业效益，能源问题不可忽视。本文从面向能源的视角出发，探讨三种网络软件化技术（SDN、NFV、NS）在现代与未来网络中的能效问题。基于此框架，我们从网络场景、控制/MANO层及节能策略三个维度对现有文献进行梳理。继而，通过对比不同文献在方法、评估方式、准则与度量属性上的差异，揭示当前研究水平。最后，我们对分类文献展开分析，总结相关经验启示，并提炼十项关键问题，为节能型软件化网络的未来研究方向提供开放式讨论。