http://www.rfc-editor.org/rfc/rfc3931.txt
RFC 3931: Layer Two Tunneling Protocol - Version 3 (L2TPv3), J. Lau, M. Townsley, I. Goyret2005-03-01T23:00:00-00:00This document describes "version 3" of the Layer Two Tunneling Protocol (L2TPv3). L2TPv3 defines the base control protocol and encapsulation for tunneling multiple Layer 2 connections between two IP nodes. Additional documents detail the specifics for each data link type being emulated. [STANDARDS-TRACK]