Software-defined networking (SDN) is a network architecture that decouples the control plane, which decides how traffic is routed, from the data plane, which forwards packets, centralising control logic in a programmable software controller. By exposing the network through open interfaces, SDN allows traffic flows and policies to be configured dynamically and programmatically rather than device-by-device. This abstraction enables automation, virtualisation and centralised orchestration of network behaviour.
Overview
- SDN replaces per-device manual configuration with centralised, programmatic control.
- A logically central controller maintains a global view of the network.
- Open southbound interfaces (such as OpenFlow) instruct forwarding devices.
- Northbound APIs let applications request network behaviour and policy.
Mechanisms
- Control plane computes forwarding decisions centrally.
- Data plane devices forward packets according to installed flow rules.
- Controller programs flows through standardised southbound protocols.
- Network applications consume northbound APIs for orchestration.
Applications
- Data-centre and cloud network automation.
- Network virtualisation and multi-tenant isolation.
- Traffic engineering and dynamic policy enforcement.
- Enabling Network Slicing in carrier networks.