Ldp Frr And Ldp-Over-Rsvp; Ldp Frr And Rsvp Shortcut (Igp Shortcut) - Alcatel-Lucent 7450 Manual

When LDP FRR is enabled in LDP and the ldp-shortcut option is enabled in the router level, in
transit IPv4 packets and specific CPM generated IPv4 control plane packets with a prefix
resolving to the LDP shortcut are protected by the backup LDP NHLFE.

LDP FRR and LDP-over-RSVP

When LDP-over-RSVP is enabled, the RSVP LSP is modeled as an endpoint, i.e., the destination
node of the LSP, and not as a link in the IGP SPF. Thus, it is not possible for IGP to compute a
primary or alternate next-hop for a prefix which FEC path is tunneled over the RSVP LSP. Only
LDP is aware of the FEC tunneling but it cannot determine on its own a loop-free backup path
when it resolves the FEC to an RSVP LSP.
As a result, LDP does not activate the LFA next-hop it learned from RTM for a FEC prefix when
the FEC is resolved to an RSVP LSP. LDP will activate the LFA next-hop as soon as the FEC is
resolved to direct primary next-hop.
LDP FEC tunneled over an RSVP LSP due to enabling the LDP-over-RSVP feature will thus not
support the LDP FRR procedures and will follow the slow path procedure of prior
implementation.
Note that when the user enables the lfa-only option for an RSVP LSP, as described in
Alternate Calculation in the Presence of IGP shortcuts on page
by LDP to tunnel an LDP FEC even when IGP shortcut is disabled but LDP-over-RSVP is enabled
in IGP.

LDP FRR and RSVP Shortcut (IGP Shortcut)

When an RSVP LSP is used as a shortcut by IGP, it is included by SPF as a P2P link and can also
be optionally advertised into the rest of the network by IGP. Thus the SPF is able of using a
7450 ESS MPLS Guide
Label Distribution Protocol
Loop-Free
562, such an LSP will not be used
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