How do controller-based networks differ from traditional networks regarding control-plane placement?

In controller-based networks (like SDN), the control plane, which makes forwarding decisions, is centralized in a software-defined network (SDN) controller. This allows for a global view of the network and simplified management. In contrast, traditional networks distribute control-plane functions across individual network devices (routers, switches). Each device runs its own routing protocols (e.g., OSPF, EIGRP) and makes independent forwarding decisions. The data plane, which handles the actual packet forwarding, remains distributed in both architectures. The incorrect options confuse the roles of the control and data planes or incorrectly describe their distribution.