SDN Provides 3 things
Where is the “state” represented on routers?
Routing Table
Where does the control plane logic live in an SDN?
In a centralized “controller”. Not on the routers individually.
2 defining characteristics of SDN
The logic for routing is in a “controller”. So that means the 2 characteristics are:
SDN Downsides/Challenges: Scalability
Each controller can be responsible for thousands of switches
SDN Downsides/Challenges: Consistency
Need to make sure each controller has the same view of the network as all other controllers