Overview
A static label switched path (LSP) is established by manually specifying the incoming label and outgoing label on each node (ingress, transit, or egress node) of the forwarding path.
Static LSPs consume fewer resources, but they cannot automatically adapt to network topology changes. Therefore, static LSPs are suitable for small and stable networks with simple topologies.
The ingress node of a static LSP performs the following operations:
Determines an FEC for a packet according to the destination address.
Adds the label for that FEC into the packet.
Forwards the packet to the next hop or out of the outgoing interface.
A transit node swaps the label carried in a received packet with a label, and forwards the packet to the next hop or out of the outgoing interface.
If PHP is not configured, an egress node pops the incoming label of a packet, and performs label forwarding according to the inner label or IP forwarding.