GMPLS extends MPLS to manage additional interface types beyond packet interfaces, such as TDM, wavelength switching, and fiber switching. It allows for establishing connection-oriented LSPs and provides routing, resource discovery, connection management, and restoration functions. GMPLS supports various interface types including packet, TDM, wavelength, and fiber switching. It faces challenges around routing, signaling, and management due to the large number of links and long setup times involved in photonic networks.