GMPLS network nodes may be connected together by many data channels or links. Each channel may be a fiber, but there may be many channels within a single link for example, separate lambdas within a WDM fiber. A pair of nodes that are connected in the data plane and that run GMPLS control plane protocols need to be able to identify and refer to each data channel in an unambiguous way that their neighbor can clearly understand. Because there is usually no one-to-one correspondence between data channels and the paths that are used for control plane communication, it is necessary for the data channels to be specifically identified at each node.

It is certainly possible to configure this information at each LSR, but as the number of data channels increases, this becomes a tremendous management overhead prone to error and completely inflexible to fibering changes within the network. The problem is handled by the Link Management Protocol (LMP) that helps switches discover the capabilities and identifiers of links that connect them. The protocol also determines the operational status of links and helps the LSRs to detect and isolate faults in optical networks where some switches do not utilize electronic components on the data path (all-optical switches are often called OOOs, or photonic cross-connects, PXCs).

This chapter describes how links are managed in a GMPLS system, and explores the peculiarities of link management in different types of transport networks with a special accent on WDM networks. The Link Management Protocol...