not have to sacrifice efficiency when doing such aggrega- tions. One mechanism for measuring and reporting on edge-to-edge TE tunnels is to use PCEP. It can report the up/down status, the detailed route, the signaled bandwidth, and the desired bandwidth of each TE tunnel to the SDN controller. The reporting from the routers can be periodic and/or following significant changes to any of the TE tunnel attributes. Core-to-core, edge-to-core, and core-to-edge measurements: Even though aggregating individual edge-to-edge traffic flows to TE tunnels cuts down on the number of measure- ments and managed entities, it is often necessary from a scaling perspective to aggregate further by using a small number of core-to-core TE tunnels for every pair of core routers. In such a scenario, it is also desirable to measure and report the edge-to-core and core-to- edge traffic flows using edge-to-core and core-to-edge TE tunnels. In a large ISP network with many more edge routers than core routers, the total number of core-to-core plus edge- to-core plus core-to-edge TE tunnels is usually significantly lower than the total number of edge-to-edge TE tunnels. The PCEP mechanism described above for measuring and reporting edge-to-edge TE tunnels may also be used for measuring and reporting core-to- core, edge-to-core, and core-to-edge TE tunnels. Individual IP link measurements: In order for the SDN controller to efficiently route edge- to-edge and core-to-core traffic, it is essential to obtain the up-to-date status of each IP link that can be on the path of the traffic flow. A mechanism to do this is to use the BGP-LS protocol that allows routers to report to the controller the up/down status, total capacity, and total reservable bandwidth per traffic class for each link in its OSPF area. Individual optical node and link measurements: Since IP links are routed over optical links, it is essential to monitor the up/down status of optical links and, if necessary, change the routing of the IP links based on that information. Measureme