Motivation for PCE Architecture inter-area/AS optimal path computation (node has partial visibility) computation of inter-area/AS diverse path (node has partial visibility) CPU-intensive path computation/global optimization backup path computation for bandwidth protection with backup capacity optimization multi-layer networks e.g. TDM network provides connectivity for client-layer (IP, MPLS, L2, etc.) absence of TED or use of non-TE-enabled IGP node outside routing domain (e.g., CE to PE path computation) network element lacks control plan or routing capability |