The packets produced by wireguard are simple ip packets containing a udp header which together specify the ip address and udp port number the packet should be handed to. Wireguard is listening on that port and receives the full ip packet. The contents of the udp part inside it are a special security header (specially designed for wireguard) plus encrypted data of original ip packet.
So no ESP, AH, or anything devised in the past. It uses a special header, custom made for wireguard. Head over to wireguard.com if you want to know more about the protocol.
-------- Original message --------
From: wireguard-request@lists.zx2c4.com
Date: 01/08/2017 14:30 (GMT+03:30)
To: wireguard@lists.zx2c4.com
Subject: WireGuard Digest, Vol 17, Issue 2
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