Distributed Control Plane (Traditional)
Individual device has their own Brain / “intelligence”.
Configuration is one device at a time. CLI was early built for manual human interaction (per vendor CLI language). Configuration is one device at a time. Engineers working over the old fashioned notepad, Copying and pasting network text standard, using obsolete machine-to-machine communication using SNMP, MIBs and OIDs.
Centralized Control Plane (SDN)
Changes the networking paradigm by removing “intelligence” from individual devices and transferring it to a central controller. In other words, network control is decoupled from forwarding and is directly programmable through a central controller using Northbound and Southbound APIs. SDN is Hard to manage via CLI, easy to manage SDN using DevNet tools)