Boutros, S., Ed., Sivabalan, S., Ed., Aggarwal, R., Ed., Vigoureux, M., Ed., and X. Dai, Ed., "MPLS Transport Profile Lock Instruct and Loopback Functions", RFC 6435, DOI 10.17487/RFC6435, November 2011, <https://www.rfc-editor.org/info/rfc6435>.