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：互联网是推动新数字世界发展的驱动力，并引发了一场革命。随着物联网（IoT）概念的兴起，几乎所有物品都连接到互联网上。然而，在传统的IP网络系统中，由于数据平面与控制平面紧密耦合，管理和配置网络在计算上非常复杂且成本高昂。为简化网络管理任务，软件定义网络（SDN）被提出，作为一种朝着外部化且逻辑集中的网络控制平面的有前景的范式转变。SDN解耦了控制平面与数据平面，并提供可编程性以配置网络。为应对该新技术的迅猛发展，本文通过描述SDN中不同层及其功能，提供了对该技术的全面概述。本文给出了一个简单而有效的SDN概述，这将为读者理解该新技术并为其领域做出贡献奠定基础。