When the mesh network is established and if you happen to run this example on ESP-WROVER-KIT boards, the RGB light indicator will show you on which layer devices are.
The pink reprents root; the yellow reprents layer 2; the red reprents layer 3; the blue reprents layer 4; the green reprents layer 5; the white reprents layer greater than 5.
Root continuously sends an On / Off control message to all devices in its routing table. Devices including root itself receive this message and do the On / Off.