Multiprotocol Label Switching (MPLS), as described in Chapter 1, is concerned with data forwarding in packet, frame, and cell networks. Chapter 2 introduced the different transport networks that are deployed or under development. Generalized MPLS (GMPLS) is concerned with merging the two concepts so that a uniform control plane can be applied to any transport technology.

Traditionally, network elements of transport networks were provisioned via manual planning and configuration. It could take days (if not weeks) to add a new service and have it operate properly because careful network planning was required, and because network downtime might be needed to reposition other services. Removing services was also slow and painful because any mistakes could affect other services. It is obvious that the larger and more sophisticated transport networks become, the more demand there will be for dynamic provisioning using some sort of control plane and, as a consequence, for traffic engineering.

This chapter examines how GMPLS came about and how the concepts of MPLS can be applied to transport networks that use non-packet technologies. The consequent changes to the MPLS signaling and routing protocols are described in Chapters 4 and 5, whereas Chapter 6 discusses the Link Management Protocol that is added to the protocol family in order to support link discovery and verification in GMPLS networks.