Generalized multiprotocol label switching: An overview of signaling enhancements and recovery techniques

Generalized multiprotocol label switching, also referred to as multiprotoco l lambda switching, is a multipurpose control plane paradigm that supports not only devices that perform packet switching, but also devices that perfo rm switching in the time, wavelength, and space domains. The development of GMPLS necessitates enhancements to existing IP signaling and routing proto cols. An overview of the Mp lambdaS concept was presented in Il], and a sum mary 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 comp anion paper in the January issue of this magazine [4]. In this article we p resent enhancements to two commonly used IP signaling protocols, RSVP and L DP, to support GMPLS. We illustrate the concept of hierarchical label switc hed path setup with an example, discuss mechanisms for bidirectional LSP se tup, and describe the applications of suggested labels. We also discuss the important problem of protection and restoration in the GMPLS context. Fina lly, we describe how various recovery mechanisms can be implemented within the GMPLS framework.