ITU-T Recommendation G.808.3 defines the generic aspects of a Shared Mesh Protection (SMP) mechanism, where the difference between SMP and Shared Mesh Restoration (SMR) is also identified. ITU-T Recommendation G.873.3 defines the protection switching operation and associated protocol for SMP at the Optical Data Unit (ODU) layer. RFC 7412 provides requirements for any mechanism that would be used to implement SMP in a Multi-Protocol Label Switching - Transport Profile (MPLS-TP) network. This document updates RFCs 4872 and 4873 to provide extensions for Generalized Multi-Protocol Label Switching (GMPLS) signaling to support the control of the SMP mechanism.