LSP

An LSP is a fixed data-forwarding path that is traversed by labeled packets through an MPLS network. An LSP starts at one PE or P device and ends at another PE or P device, and consists of a sequence of LSP hops in which a packet travels from core device to core device through a label switching mechanism.

An LSP can be established dynamically in one of two ways:

1. Based on standard routing protocols and Label Distribution Protocol (LDP) signaling

2. Based on constraint-based routing algorithms and a signaling protocol such as Resource Reservation Protocol with traffic engineering extensions (RSVR-TE).

   LSPs that are established by using the first method are called LDP LSPs. LSPs that are established by using the second method are called TE LSPs or subLSPs.

   MPLS Manager uses the “LSP” class to represent the discovered LSP types that are listed in LSP types discovered by MPLS Manager.

Table 1. LSP types discovered by MPLS Manager

LSP type	DisplayName prefix assigned to discovered instance	Description
TE tunnel	TETunnel-	An RSVP-TE signaled point-to-point MPLS tunnel. A TE tunnel has no LSP hops and is not directly associated with any interfaces.
TE LSP	(none)	Associated with a TE tunnel. For a link/node protected TE tunnel, the primary and backup TE LSPs start at an ingress PE or P device, traverse one or more P devices, and end at an egress PE or P device. For a path-protected TE tunnel, the primary and secondary LSPs start at an ingress PE device, traverse one or more P devices, and end at an egress PE.
P2MP LSP	P2MP-	An RSVP-TE signaled point-to-multipoint MPLS P-tunnel. A P2MP LSP has no LSP hops and is not directly associated with any interfaces.
subLSP	subLSP-	Associated with a P2MP LSP. A subLSP starts at an ingress PE device, traverse one or more P devices, and ends at an egress PE device.
LDP LSP	LSP-	An LDP-signaled point-to-point LSP. An LDP LSP starts at an ingress PE device, traverses one or more P devices, and ends at an egress PE.

MPLS Manager discovers LDP LSPs in the context of VPNs. Thus, for L2VPNs, MPLS Manager discovers only those LDP LSPs between PE devices that have pseudowires configured between them. For L3VPNs, MPLS Manager discovers only those LDP LSPs between PE devices that have VPN routes configured between them. In situations where not all of the devices in the MPLS network are managed by MPLS Manager, a discovered LDP LSP might represent something less than the entire LSP path.

In a Huawei or Juniper ERX environment, MPLS Manager discovers at most one bidirectional pair of VPN-related LDP LSPs for each pair of PE devices. In a Cisco or Juniper M/T environment, MPLS Manager discovers all VPN-related LDP LSPs, and discovers all TE tunnels and all TE LSPs.