SD-WAN creates an overlay network on top of existing WAN connections.
Components:
Edge devices. Sit at branch sites. Terminate tunnels, measure link quality, steer traffic.
Controller. Central management. Distributes policies, collects telemetry.
Orchestrator. Web interface for configuration and monitoring.
Overlay tunnels: IPsec encrypted, dynamic path selection, automatic failover, bandwidth aggregation.
Traffic steering:
Identify application via DPI
Check policy for that application
Measure available paths
Select best path meeting SLA requirements