http://www.rfc-editor.org/rfc/rfc3077.txt
RFC 3077: A Link-Layer Tunneling Mechanism for Unidirectional Links, E. Duros, W. Dabbous, H. Izumiyama, N. Fujii, Y. Zhang2001-03-01T23:00:00-00:00This document describes a mechanism to emulate full bidirectional connectivity between all nodes that are directly connected by a unidirectional link. [STANDARDS-TRACK]