These two objects are required to uniquely identify an LSP-PATH within an LSP:
Tunnel ID (2 octets). This field contains a unique value generated by the ingress router of the LSP. This helps distinguish the particular LSP from other paths originating at the same ingress router. The selected value remains constant throughout the life of the LSP. It's part of the SESSION Object.
LSP ID (2 octets). This field also contains a unique value generated by the ingress router of the LSP. This helps distinguish the particular sender and its resources from other paths originating at the same ingress router for the same RSVP session. The LSP-ID is located in the SENDER_TEMPLATE(Path Message)/ Filter Spec (Resv Message) Object.
Topology:
The router loopback is configured as 10.0.0.x/32 where x is the router number.
MPLS RSVP LSP has been configured from R1 to R4. The name of the LSP is R1_TO_R4. From the following command, we can verify the Tunnel-id and the LSP-id:
root@R1> show rsvp session extensive name R1_TO_R4 Ingress RSVP: 1 sessions 10.0.0.4 From: 10.0.0.1, LSPstate: Up, ActiveRoute: 0 LSPname: R1_TO_R4, LSPpath: Primary LSPtype: Static Configured Suggested label received: -, Suggested label sent: - Recovery label received: -, Recovery label sent: 299936 Resv style: 1 FF, Label in: -, Label out: 299936 Time left: -, Since: xxxxxxxxxxxx Tspec: rate 0bps size 0bps peak Infbps m 20 M 1500 Port number: sender 5 receiver 59554 protocol 0 <<<< Tunnel-id 59554 LSP-id 5 Enhanced FRR: Enabled (Downstream) PATH rcvfrom: localclient Adspec: sent MTU 1500 Path MTU: received 1500 PATH sentto: 10.1.2.2 (ge-0/0/1.12) 1 pkts outgoing message state: refreshing, Message ID: 33, Epoch: 5860194 RESV rcvfrom: 10.1.2.2 (ge-0/0/1.12) 1 pkts, Entropy label: Yes incoming message handle: R-21/1, Message ID: 53, Epoch: 5860203 Explct route: 10.1.2.2 10.2.3.3 10.3.4.4 Record route: <self> 10.1.2.2 10.2.3.3 10.3.4.4 Total 1 displayed, Up 1, Down 0 Egress RSVP: 1 sessions Total 0 displayed, Up 0, Down 0 Transit RSVP: 0 sessions Total 0 displayed, Up 0, Down 0 root@R1>
Below is the packet capture done on R4: