Huawei Huawei Huawei Grotto Networking CATR Generalized Multiprotocol Label Switching (GMPLS) can be used to control a wide variety of technologies including packet switching (e.g., MPLS), time division (e.g., Synchronous Optical Network / Synchronous Digital Hierarchy (SONET/SDH) and Optical Transport Network (OTN)), wavelength (lambdas), and spatial switching (e.g., incoming port or fiber to outgoing port or fiber). In some of these technologies, network elements and links may impose additional routing constraints such as asymmetric switch connectivity, non- local label assignment, and label range limitations on links. This document describes Open Shortest Path First (OSPF) routing protocol extensions to support these kinds of constraints under the control of GMPLS.