The Internet is the driving force of the new digital world, which has created a revolution. With the concept of the Internet of Things (IoT), almost everything is being connected to the internet. However, with the traditional IP network system, it is computationally very complex and costly to manage and configure the network, where the data plane and the control plane are tightly coupled. In order to simplify the network management tasks, software-defined networking (SDN) has been proposed as a promising paradigm shift towards an externalized and logically centralized network control plane. SDN decouples the control plane and the data plane and provides programmability to configure the network. To address the overwhelming advancement of this new technology, a holistic overview of SDN is provided in this paper by describing different layers and their functionalities in SDN. The paper presents a simple but effective overview of SDN, which will pave the way for the readers to understand this new technology and contribute to this field.

翻译：互联网是新数字世界的推动力,它创造了一场革命。随着物联网(IoT)的概念,几乎所有东西都与互联网连接起来。然而,传统的IP网络系统,管理和配置网络是计算上非常复杂和昂贵的,数据平面和控面是紧密结合的。为了简化网络管理任务,软件定义的网络(SDN)被提议为向外部和逻辑集中的网络控制平面转变的有希望的范式转变。SDN解开控制平面和数据平面,并提供配置网络的可编程性。为了解决这一新技术的巨大进步,本文通过描述SDN的不同层次及其功能,对SDN进行了全面的概述。本文对SDN作了简单而有效的概述,这将为读者了解这一新技术并为这个领域作出贡献铺平道路。