s to be built when and where the demand mate- rializes, eliminating forecasting error and ultimately improving utilization and customer experience. The process of creating a new L3 trunk requires convergence of the management and control of the L0 and L3 networks. The high-level steps are as follows: 1. Build and inventory the tail (router port cabled to transponder). 2. Build the end-to-end optical wavelength between the two desired routers. This will be done via the ROADM Node Controller (RNC). Add L3 configurations including activating routing protocols, assigning metrics, activating link failure detection mechanisms, etc. 4. Add the trunk to an existing LAG or create a new LAG. Figure 13.23 shows the high-level design for the multi-layer controller. It builds on the capabili- ties put in place for centralized traffic engineering and adds control of the L0 network via an inter- face to the ROADM Node Controller and configuration management of the L3 packet routers via a Netconf/YANG interface. This fast provisioning process under SDN control can be applied to failure situations also. Trunks that fail due to a fiber cut or an OA failure can be rerouted over a fiber path that is intact. Or, it may be necessary to configure additional trunks between other nodes to provide an alternate path for the traffic on the failed link. The overall result would be to reduce the number of active trunks that are needed to carry traffic for both normal and failure events. Even when you include the additional tails needed to create these restoration trunks, because of the sharing between all possible directions out of an office, the network has less equipment and less cost overall. SDN can also be used for even more complex control involving customer trunks that are access- ing packet services. With virtual PE functions distributed across all of the AIC nodes in the net- work, and customer packet service homing onto a particular PE in a particular office, if there is a fiber failure on the link connecting the office, the traffic