What is an essential characteristic of software-defined networks (SDN)?

An essential characteristic of software-defined networks (SDN) is centralized network control. In an SDN architecture, the control plane is decoupled from the data plane, allowing a centralized controller to manage and direct the network's data flow. This centralized approach provides network administrators with greater flexibility and control over the network, enabling them to easily provision, manage, and monitor the network resources.

Centralized control in SDN allows for automated responses to network conditions, dynamic reconfiguration, and the ability to implement policies consistently across the network. This capability is fundamental to the SDN model, as it empowers organizations to respond rapidly to changing business needs and enhances operational efficiency.

In contrast, other characteristics do not align with the core principles of SDN. For example, static routing capabilities are typically associated with traditional networking, which does not benefit from the dynamism and programmability that SDN provides. While SDN can lead to lower costs due to reduced hardware dependency and efficient resource management, cost is not a defining characteristic of the architecture itself. Lastly, any suggestion of increased physical hardware requirements contradicts the SDN goal of minimizing reliance on physical devices by allowing more network functions to occur in software.