What is the purpose of a southbound API in a control based networking architecture?

In a control-based networking architecture, the term "southbound API" refers to an interface or set of protocols that allow communication between the control plane and the data plane components of the network devices. This communication is essential for the central controller to convey instructions and policies to the network devices, enabling them to forward traffic based on the controller's decisions. The term "southbound" signifies the direction of communication from the central controller down to the network devices.

The purpose of a southbound API in a control-based networking architecture includes:

1. Control Plane Communication:

   • The southbound API enables the communication between the control plane, typically represented by the SDN (Software-Defined Networking) controller, and the data plane of network devices. The control plane is responsible for making decisions about how traffic should be forwarded in the network.

2. Policy Enforcement:

   • The southbound API allows the SDN controller to push network policies, configurations, and rules to the network devices. These policies define how traffic should be treated, the quality of service (QoS) parameters, access control rules, and other aspects of network behavior.

3. Dynamic Network Adaptation:

   • Through the southbound API, the controller can dynamically adapt the behavior of network devices based on changing network conditions, traffic patterns, or specific events. This adaptability is a key feature of SDN, allowing for more responsive and flexible network management.

4. Flow Installation and Modification:

   • The controller uses the southbound API to instruct network devices on how to handle specific flows of traffic. It can install flow entries in the flow tables of switches, routers, or other devices, specifying how packets matching certain criteria should be processed.

5. Programmability:

   • Southbound APIs provide a standardized way for the SDN controller to programmatically interact with diverse network devices. This promotes interoperability and allows network administrators to manage and control a heterogeneous network infrastructure through a centralized controller.

6. Abstraction of Network Complexity:

   • The southbound API abstracts the complexity of individual network devices. Instead of dealing with the specifics of each device's operating system or configuration syntax, the controller communicates using a standardized interface, simplifying network management tasks.