wavelength channels are nested into the fiber label, on the right (b) labels relative to different MPLS LSPs are nested into the wavelength path label. Convergent Network Management and Control Plane In particular in Figure 8.10a, a set of wavelengths are nested into a fiber link by nesting the labels associated with wavelength channels resources into the label associated to the fiber channel. This kind of nesting allows the wavelength channels to be considered as a single entity, to be routed always together, switched together and protected together. This kind of nest- ing is useful, for example, if a Gbit/s virtual channel is transmitted as a group of four 20 Gbit/s channels. In this case, the association made through GLSPs nesting within the same layer allows the 100 Gbit/s channel to be recognized as a single entity by the network even if it is constituted by parallel wavelength channel. Another case in which nesting wavelength into a fiber channel is useful when a client layer requires a SLA prescribing the same network traversing time for different wave- length channels. This can be achieved by nesting them into the same GLSP. In Figure 8.10b the nesting of several MPLS LSPs into a lower layer wavelength channel is shown. Physically the GLSPs are multiplexed into a wavelength channel using OTN frame and GFP adaptation, under a logical point of view, in order to recognize that the GLSPs will travel the network in the same route, a GLSP is built nesting the individual layer two labels into a layer one label attached to the wavelength channel resources. In general, ordering GLSPs hierarchically within a network layer requires that GLSP are encoded in a hierarchical way. A natural GLSP hierarchy can be established based on interface types and it is also the hierarchy used to build the examples of Figure 8.10. At the top of this hierarchy are FSC interfaces followed, in decreasing order, by LSC, TDM, L2SC, and PSC interfaces. This order is because wavelengths can be encapsulated within a fiber, time slots in wav