Weingarten, Y., Bryant, S., Ceccarelli, D., Caviglia, D., Fondelli, F., Corsi, M., Wu, B., and X. Dai, "Applicability of MPLS Transport Profile for Ring Topologies", RFC 6974, DOI 10.17487/RFC6974, July 2013, <https://www.rfc-editor.org/info/rfc6974>.