There are specific requirements for the support of networks comprising Label Switching Routers (LSRs) participating in different data plane switching layers controlled by a single Generalized Multi-Protocol Label Switching (GMPLS) control plane instance, referred to as GMPLS Multi-Layer Networks / Multi-Region Networks (MLN/MRN). This document defines extensions to GMPLS routing and signaling protocols so as to support the operation of GMPLS Multi-Layer / Multi-Region Networks. It covers the elements of a single GMPLS control plane instance controlling multiple Label Switched Path (LSP) regions or layers within a single Traffic Engineering (TE) domain. [STANDARDS-TRACK]