Step 1: Establish the Initial LSP Tunnel

The ingress router uses the Path message to request that the egress router set up the initial LSP tunnel with the SE reservation style. When establishing the initial LSP tunnel, the ingress and egress routers perform the following actions:

1. The ingress router includes the following in the initial Path message:

• A LSP Tunnel IPv4 Session object that contains the following:

• IPv4 address of the egress node.
• Tunnel ID that remains constant for the life of the LSP tunnel between the ingress and egress routers.
• Extended Tunnel ID that identifies the ingress router's IPv4 address.

• The SE reservation style in the Session Attribute object.
• A Sender Template object that contains the following:

• The IPv4 address of the sender (ingress) node.
• A LSP ID that can change in the future, when the LSP needs to be rerouted, allowing the ingress router to appear as a different sender so it can share resources with itself (see the LSP ID field of the LSP Tunnel IPv4 C-type extension for the Sender Template and Filter Spec objects).

2. Upon receipt of the Path message, the egress router sends a Resv message with an SE reservation style toward the ingress router.
3. When the ingress router receives the Resv message, the initial LSP tunnel is established with an SE reservation style.