The Generalized Multi-Protocol Label Switching (GMPLS)[1] is a protocol suite extending MPLS to manage further classes of interfaces and switching technologies other than packet interfaces and switching, such as time division multiplex, layer-2 switch, wavelength switch and fiber-switch.
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Generalized MPLS differs from traditional MPLS[2] in that it supports multiple types of switching, i.e., the addition of support for TDM, wavelength, and fiber (port) switching. The support for the additional types of switching has driven GMPLS to extend certain base functions of traditional MPLS and, in some cases, to add functionality.
These changes and additions impact basic LSP properties: how labels are requested and communicated, the unidirectional nature of LSPs, how errors are propagated, and information provided for synchronizing the ingress and egress LSRs.
GMPLS is based on Generalized Labels. The Generalized Label is a label that can represent either (a) a single fiber in a bundle, (b) a single waveband within fiber, (c) a single wavelength within a waveband (or fiber), or (d) a set of time-slots within a wavelength (or fiber). The Generalized Label can also carry a label that represents a generic MPLS label, a Frame Relay label, or an ATM label.
GMPLS is composed of three main protocols: