How does software-defined networking differ from virtual networking?

The architecture of a software-defined network (SDN) is designed with a separation between the control plane and the data plane (user plane). What this means is that the processing of network functions takes place somewhere other than the physical devices that are carrying the data packets to far-flung parts of the world. Centrally-managed SDN controllers dictate traffic flows and allow for agile and flexible management of the network.

The SDN architecture has three layers:

• Application layer
• Control layer
• Infrastructure layer

SDN is being strongly promoted by the Open Networking Foundation. The idea is to replace proprietary network equipment with off-the-shelf, white box switches. Linux-based servers can be configured with software to create virtual environments.

Virtual networking, on the other hand, may refer to a number of implementations. The traditional idea of a virtual network has been one that connects wide area network components using virtual links, such as VCs, VLANs or VPNs. In today’s evolving IT infrastructures, other developments lean toward different descriptions for the term. Some vendors have created virtual services switches or platforms that consolidate diverse services and functions. The aim is to simplify network infrastructure through virtualization. One of the key aspects of virtual networking is the disaggregation of software and hardware.

Overlay virtualization is a solution that is becoming more common. A form of virtual networking, topographies with no links to physical devices allow for private connections between isolated network segments. The flexibility of overlay networks makes it possible to run a variety of network traffic among virtual components in cloud computing environments. Not only virtual machines comprise this architecture, but virtualized switches, routers, firewalls, load balancers and other network appliances are possible through network functions virtualization (NFV).
 

软件定义网络（SDN）的架构设计为控制平面和数据平面（用户平面）分离。这意味着网络功能的处理发生在将数据包传送到世界各地的物理设备之外的其他地方。集中管理的 SDN 控制器控制流量并实现敏捷、灵活的网络管理。

SDN架构分为三层：

• 应用层
• 控制层
• 基础设施层

开放网络基金会正在大力推动SDN 。这个想法是用现成的白盒交换机取代专有网络设备。基于Linux的服务器可以通过软件进行配置来创建虚拟环境。

另一方面，虚拟网络可以指多种实现方式。虚拟网络的传统理念是使用虚拟链路（例如 VC、VLAN或VPN）连接广域网组件。在当今不断发展的 IT 基础设施中，其他发展倾向于对该术语的不同描述。一些供应商创建了虚拟服务交换机或平台来整合不同的服务和功能。目的是通过虚拟化简化网络基础设施。虚拟网络的关键方面之一是软件和硬件的分解。

覆盖虚拟化是一种越来越常见的解决方案。虚拟网络的一种形式，没有物理设备链接的拓扑允许隔离网段之间的专用连接。覆盖网络的灵活性使得在云计算环境中的虚拟组件之间运行各种网络流量成为可能。该架构不仅包括虚拟机，还可以通过网络功能虚拟化(NFV) 实现虚拟化交换机、路由器、防火墙、负载均衡器和其他网络设备。