The infrastructure layer is the device layer of a software-defined networking (SDN) architecture. It contains routers and switches that execute instructions received from the control layer, while message forwarding remains distributed across those devices. section 22.2.2 section 22.4
Understand its operational boundaries:
- Receives actionable forwarding instructions from the Control Layer rather than independently determining all network behavior. section 22.2.2
- Connects to the Control Layer through the southbound interface (SBI), which can use OpenFlow, NETCONF, OpFlex, SSH, or SNMP. section 22.4
- Forms the physical foundation of the SDN fabric, supporting virtual overlay networks over the physical underlay. section 22.4
Forwarding under centralized control
A controller translates high-level network requirements into instructions and distributes them to routers and switches in the infrastructure layer. Those devices then forward messages according to the received instructions. section 22.2.2
Figure 22.6 The three layers of SDN architecture: Application, Control, and Infrastructure. The NBI facilitates communication between the Application and Control Layers, and the SBI facilitates communications between the Control and Infrastructure Layers.
Use the architecture diagram to trace the infrastructure layer’s position below the Control Layer and follow SBI communication between them. section 22.2.2
