Graceful shutdown is used to maintain selective links and nodes in a TE network. Before a shutdown, head-end LER nodes are notified of the imminent shutdown of the links or nodes for the purpose of maintenance, so the head-end nodes can move the paths of the LSPs away from the affected resources. Modified TE parameters for the affected links are flooded so all other nodes in the network avoid them in the CSPF calculations.
When the maintenance is over, the operator disables graceful shutdown, which reinstates and floods the user-configured TE parameters. The restored links are available for LSP path establishment.