 UNI defines two LMP extensions: In-band control channel bootstrap This is a way of initiating in- band control channel communication when the IP address of a neighboring node is not known. The idea is that when a control channel is realized in band over a data link, an OIF UNI LMP node can send its initial LMP Config message to the All Nodes multicast address rather than to a specific unicast IP address. This enables an LMP node to automatically determine which IP address to use when communicating with its neighbor. Service discovery This is a way for UNI client and network nodes to discover each other's UNI capabilities via the exchange of ServiceConfig, ServiceConfigAck, and ServiceConfigNack messages. Using this mechanism, A UNI client node indicates its support for port-level attributes such as link type, signal type, and transparency. A UNI network node indicates its support for particular signaling protocols, transparency and monitoring, and network diversity. In summary, optical networking is an important and challenging domain for development and experimentation using the GMPLS protocols. Con- versely, the use of GMPLS and LMP is a major step forward for optical net- work providers who have historically been troubled by interoperability problems resulting from nonstandardized control and management protocols. The application of GMPLS to the optical network has thrown up a num- ber of interesting technical challenges. This paper has described some of those challenges and presented explanations, examples of how those chal- lenges can be addressed in practice, and, in particular, how aspects of the GMPLS protocol have evolved to meet those challenges. End Notes 1. Peter Ashwood-Smith et al., "Generalized MPLS-Signaling Functional Description," draft-ietf-mpls-generalized-signaling-07.txt, November 2001. GMPLS in Optical Networks 2. This section was contributed by Data Connection Ltd. (DCL) based on Neil Jerram and Adrian Farrel's paper "MPLS in Optical Networks- An Analysis of the Features of MPLS and Gener