Power over Ethernet is a family of IEEE 802.3 standards that define power provisioning to a network device through the twisted pair network cable.
Power delivery is negotiated using MDI signaling (layer 1) or LLDP (layer 2). 802.3af can provide up to 13 W, 802.3at up to 25 W, and 802.3bt (4PPoE) up to 50 W/71 W using two/four pairs.
