http://www.rfc-editor.org/rfc/rfc4591.txt
RFC 4591: Frame Relay over Layer 2 Tunneling Protocol Version 3 (L2TPv3), M. Townsley, G. Wilkie, S. Booth, S. Bryant, J. Lau2006-08-01T23:00:00-00:00The Layer 2 Tunneling Protocol, Version 3, (L2TPv3) defines a protocol for tunneling a variety of data link protocols over IP networks. This document describes the specifics of how to tunnel Frame Relay over L2TPv3, including frame encapsulation, virtual-circuit creation and deletion, and status change notification. [STANDARDS-TRACK]