Networks, with Reference to the Link Management Protocol and Optical UNI," Data Connection Ltd. White Paper, Version 2, October 2001. 16. Do not confuse this with forward error correction (FEC). 17. C. Metz, "A Survey of Advanced Internet Protocols," Cisco Educational Materials, 2001. This page intentionally left blank. GMPLS in Optical Networks Chapter 8 One of the most exciting recent developments in optical networks has been the attempt to standardize a generalized version of the multiprotocol label switching (MPLS) architecture so that it can be used to signal paths through an optical network. In a classical MPLS network, incoming packets are assigned a label by a label edge router (LER). Packets are forwarded along a label-switched path (LSP) where each label-switched router (LSR) makes forwarding decisions based solely on the contents of the label. At each hop, the LSR strips off the existing label and applies a new one that tells the next hop how to forward the packet. RFC 3031 "MPLS Architecture" has a detailed explanation of this process. However, classical MPLS labels are carried in the header of each cell or packet that flows through the MPLS network. Optical switches, on the other hand, forward large streams of data without decomposing them into packets or cells so the header-based labels of classical MPLS cannot tell an optical switch how to switch that data flow. Hence, the need for MPLS to be generalized, as the Internet Engineering Task Force (IETF) specification of Generalized MPLS (GMPLS) explains, is as follows.1 The original architecture has recently been extended to include LSRs whose forwarding plane recognizes neither packet nor cell boundaries, and therefore cannot forward data based on the information carried in either packet or cell headers. Specifically, such LSRs include devices where the for- warding decision is based on time slots, wavelengths, or physical ports. Given the previous information, LSRs (or interfaces on LSRs) can be sub- divided into the following groups: Interfaces tha