Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 93)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 69
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Adaptive Fast Reroute (FRR) and Global Revertiveness
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Adaptive Fast Reroute (FRR) and Global Revertiveness
Adaptive capabilities support to Fast Reroute (FRR) and enabling global revertiveness enables the
following capabilities:
• Once FRR is triggered, a make-before-break operation is performed to reestablish the primary
path. When an established path attempts to reroute onto a new path, the ingress device
maintains existing paths and allocated bandwidths, ensuring that the existing path is not
prematurely torn down and allowing the current traffic to continue flowing while the new path
is set up.
• Configuration of the secondary path to have the LSP re-trigger the primary path is no longer
required.
• The LSP waits for the configured revertive hold time after FRR is triggered before trying to
re-optimize.
Figure 17 shows an example of a primary LSP between A-B-C and backup over bypass tunnel on the
path A-D-C. The primary LSP is configured without a strict path. When the interface between A-B
goes down, the global revertiveness feature triggers a new LSP on the path A-E-C. The traffic is
shifted to the new instance and old instance is torn down.
When the primary LSP is triggered with strict path (A-B-C), after global revertiveness is triggered, a
new instance tries the same path given in the strict path. In
Figure 17 , new instance also tries to
come up in the path A-B-C.
FIGURE 17 Sample topology for global revertiveness