 also be used to further improve the granularity and timeliness of data the controller can access. The SDN controller will be invoked by network changes communicated via the BGP-LS and PCEP protocols. The SDN controller will analyze the routing performed by the distributed pro- tocols and decide whether there is a better way to route the tunnels to make use of the available network capacity as indicated by the BGP-LS protocol. Heuristic algorithms can perform such calculations in a subsecond timeframe and yet come very close to the theoretical optimal solution. 13.3.2 MULTILAYER CONTROL Centralizing TE will have some positive impact to network performance, but it is even more exciting to look at the possibility of converging the management and control of the L3 and flexible optical network. Flexible ROADMs allow the optical segment of new trunks between routers to be rapidly provi- sioned. The need for new trunks could be due to traffic spikes or steady organic growth across all Network Core packet services. In order to take advantage of this automation, "tails"-which consists of a 100G router port cabled to a transponder, must be prebuilt. The SDN control uses these pools of tails to be able to automatically create new trunks without manual intervention. The tail can be used to create a trunk in any direction out of the router office. Today's capacity management process attempts to forecast the traffic demands between specific city-pairs several months into the future. The forecast is then implemented by engineering, order- ing, and implementing capacity between these city-pairs. Once in place, the capacity is static. The actual traffic patterns inevitably differ from the forecast. Flexible ROADMs allow us to vastly simplify the capacity management process. Today's process in which we forecast and build capacity between city-pairs (a N2 problem) can be replaced with a simple consumption model in which we manage an inventory of tails in each of the N core offices. SDN-controllable ROADMs allow end-to-end L3 trunk