http://www.rfc-editor.org/rfc/rfc3145.txt
RFC 3145: L2TP Disconnect Cause Information, R. Verma, M. Verma, J. Carlson2001-07-01T23:00:00-00:00This document provides an extension to the Layer 2 Tunneling Protocol ("L2TP"), a mechanism for tunneling Point-to-Point Protocol (PPP) sessions. [STANDARDS-TRACK]