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7.3.2. Northbound and Southbound APIs
| API | Direction | Purpose |
|---|---|---|
| Northbound | Controller ↔ Applications | Expose network capabilities to apps |
| Southbound | Controller ↔ Devices | Push configurations, collect data |
Southbound protocols: OpenFlow (the original SDN protocol—the controller writes entries directly into each device's flow/forwarding table), NETCONF and RESTCONF (model-driven configuration), and legacy CLI over SSH or SNMP. Northbound APIs are typically REST. A third direction, east-west, links controllers to one another (clustering and redundancy)—it faces neither the applications nor the devices.
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Written byAlvin Varughese
Founder•20 professional certifications