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MPLS and RSVP

7210 SAS M, T, X, R6, Mxp MPLS Configuration Guide Page 25

PLR Bypass LSP Selection Rules

Figure 3: Bypass Tunnel Nodes

The PLR uses the following rules to select a bypass LSP among multiple manual and dynamic

bypass LSP’s at the time of establishment of the primary LSP path or when searching for a bypass

for a protected LSP which does not have an association with a bypass tunnel:

1. The MPLS/RSVP task in the PLR node checks if an existing manual bypass satisfies the

constraints. If the path message for the primary LSP path indicated node protection

desired, which is the default LSP FRR setting at the head end node, MPLS/RSVP task

searches for a node-protect’ bypass LSP. If the path message for the primary LSP path

indicated link protection desired, then it searches for a link-protect bypass LSP.

2. If multiple manual bypass LSPs satisfying the path constraints exist, it will prefer a

manual-bypass terminating closer to the PLR over a manual bypass terminating further

away. If multiple manual bypass LSPs satisfying the path constraints terminate on the

same downstream node, it selects one with the lowest IGP path cost or if in a tie, picks the

first one available.

3. If none satisfies the constraints and dynamic bypass tunnels have not been disabled on

PLR node, then the MPLS/RSVP task in the PLR will check if any of the already

established dynamic bypasses of the requested type satisfies the constraints.

4. If none do, then the MPLS/RSVP task will ask CSPF to check if a new dynamic bypass of

the requested type, node-protect or link-protect, can be established.

5. If the path message for the primary LSP path indicated node protection desired, and no

manual bypass was found after Step 1, and/or no dynamic bypass LSP was found after 3

attempts of performing Step 3, the MPLS/RSVP task will repeat Steps 1-3 looking for a

suitable link-protect bypass LSP. If none are found, the primary LSP will have no

protection and the PLR node must clear the “local protection available” flag in the IPv4

address sub-object of the RRO starting in the next Resv refresh message it sends

upstream.

6. If the path message for the primary LSP path indicated link protection desired, and no

manual bypass was found after step 1, and/or no dynamic bypass LSP was found after

performing Step 3, the primary LSP will have no protection and the PLR node must clear

the “local protection available” flag in the IPv4 address sub-object of the RRO starting in

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