elengths, data link layer frames in time slots, and finally network layer packets in data link layer frames. As such, an GLSP starting and ending on PSC interfaces can be nested within higher ordered GLSPs. 8.3.2 GMPLS Protocol Suite Protocols of the GMPLS protocol suite can be divided into three distinct sets based on their functionality: 1. Routing protocols must be implemented by the MLCP to disseminate the network topology and its traffic engineered (TE) attributes. For this purpose, open short- est path first (OSPF) with TE extensions (OSPF-TE) or intermediate system to intermediate system (IS-IS) are currently defined. To account for multiple layers, however, GMPLS needs to add some minor extensions to these existing proto- cols. The GMPLS routing process using OSPF-TE is explained in the following sections. 2. Signaling protocols are concerned with establishing, maintaining, and removing network state (i.e., setting up and tearing down GLSPs). For signaling, GMPLS can use either Resource ReSerVation Protocol (RSVP) with TE extensions (RSVP-TE) or constraint-based routing-label distribution protocol (CR-LDP). Again, supporting multiple layers requires some extensions to existing protocols. 3. Link management is performed by a new protocol called the link management pro- tocol (LMP), which has been defined within the GMPLS standard. LMP can be used by GMPLS network elements to discover and monitor their network link connectivity. To enable link discovery between an optical switch and an optical line system, LMP has been further extended, creating LMP-WDM. Telecommunication Networks In the following subsections, the working of the most used among the protocols of the GMPLS protocol suite will be described in some detail SO as to give an idea of how GMPLS implements its functionalities. 8.3.2.1 Open Shortest Path First with Traffic Engineering To enable automated configuration of the controlled network, GMPLS defines an intrado- main routing process. Via this routing process, the network topology and its TE at