Generalized Multiprotocol Label Switching: An Overview of Signaling Enhancements and Recovery Techniques

Generalized multiprotocol label switching, also referred to as multiprotocol lambda switching, is a multipurpose control plane paradigm that supports not only devices that perform packet switching, but also devices that perform switching in the time, wavelength, and space domains. The development of GMPLS necessitates enhancements to existing IP signaling and routing protocols. An overview of the MPlS concept was presented in [1], and a summary of the extensions to IP routing protocols (OSPF [2] and IS-IS [3]) and the new Link Management Protocol to support GMPLS were presented in a companion paper in the January issue of this magazine [4]. In this article we present enhancements to two commonly used IP signaling protocols, RSVP and LDP, to support GMPLS. We illustrate the concept of hierarchical label switched path setup with an example, discuss mechanisms for bidirectional LSP setup, and describe the applications of suggested labels. We also discuss the important problem of protection and restoration in the GMPLS context. Finally, we describe how various recovery mechanisms can be implemented within the GMPLS framework.