Software-defined networking (SDN) is an approach to network virtualization that seeks to optimize network resources and quickly adapt networks to changing business needs, applications, and traffic. It works by separating the network's control plane and the data plane, creating software-programmable infrastructure that is distinct from physical devices.

With SDN, the functions of network orchestration, management, analytics, and automation become the job of SDN controllers. Because these controllers are not networking devices, they can take advantage of the scale, performance, and availability of modern cloud computing and storage resources. Increasingly, SDN controllers are built on open platforms, using open standards and open APIs, enabling them to orchestrate, manage, and control network equipment from different vendors.

SDN delivers a wide array of business benefits. Separation of the control and transport layers increases flexibility and accelerates time-to-market for new applications. The ability to respond more swiftly to issues and outages improves network availability. And programmability makes it easier for IT organizations to automate network functions, reducing operating costs.

SDN dovetails with another technology, Network Functions Virtualization (NFV). NFV offers the ability to virtualize appliance-based network functions such as firewalls, load balancers, and WAN accelerators. The centralized control that SDN provides can efficiently manage and orchestrate virtual network functions that are enabled by NFV.