If an implicit null label on the PHP node is not used, a replication segment is needed on the MP to pop the facility protection label and forward the underlying traffic based on the tree SID label.
In Figure: Protection using the actual label at the PHP node, node A is protecting the A-B link through node C, so the facility protection tunnel is set up through node C. Node C is a PHP node and is programmed to swap the facility protection label with label 3000.
After a failure on link A-B, node A pushes label 2000 as indicated by the protection next-hop programmed in the replication segment for trees 1 and 2. The packet is forwarded to node C, where node C swaps the protection label with label 3000 for both tree 1 and tree 2, and forwards the packet to node B. Node B has a replication segment for the facility protection tunnel, which has an action of pop 3000. After popping 3000 on node B, the tree SID label for label 1 and label 2 is exposed and the corresponding replication segment is found and executed.
