A distributed control plane places network intelligence in individual devices. Each router runs a routing protocol, communicates with neighbors, and independently calculates the best route to learned destinations. section 22.2.2
Core behavior and contrast:
- Routers use protocols such as OSPF to learn routes and build their own routing tables. section 22.4
- Unlike a centralized control plane, no controller performs the routing calculations for every device; control functions remain distributed. section 22.2.2
- The control plane determines forwarding behavior, while the data plane remains responsible for receiving, processing, and forwarding messages. section 22.4
Figure 22.5 SDN architecture centralizes the Control Plane functions in the controller. However, the Data Plane functions (message forwarding) remain distributed among each network device.
Compare distributed control functions with SDN’s centralized controller while observing that message forwarding remains distributed across devices. section 22.2.2
