Northbound APIs let applications communicate with the SDN controller.
Common API types:
REST APIs. HTTP-based interfaces for configuration and queries. Most controllers expose RESTCONF.
gRPC. High-performance RPC framework with lower overhead.
Native libraries. Language-specific bindings for direct communication.
What applications can do:
- Query network topology and state
- Request paths between endpoints
- Create network policies
- Define intents (what you want, not how)
- Monitor traffic statistics
- Receive event notifications
Applications request network behavior without knowing device details.