FortiAP units can be connected to the WiFi controller by Ethernet or by WiFi. In the latter case, you configure a special backhaul network, the mesh, that carries traffic and control signals between FortiAP units and the WiFi controller. Regular WiFi clients cannot connect to the mesh network, they can connect only to non-mesh SSIDs. The mesh network is useful when running Ethernet cables is not practical. For best results, the mesh network should use a dedicated radio at both the WiFi controller and FortiAP unit. Otherwise, the client SSIDs compete for bandwidth with the mesh backhaul.