http://www.rfc-editor.org/rfc/rfc7571.txt
RFC 7571: GMPLS RSVP-TE Extensions for Lock Instruct and Loopback, J. Dong, M. Chen, Z. Li, D. Ceccarelli2015-07-01T23:00:00-00:00This document specifies extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) to support Lock Instruct (LI) and Loopback (LB) mechanisms for Label Switched Paths (LSPs). These mechanisms are applicable to technologies that use Generalized MPLS (GMPLS) for the control plane.