Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 215)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 191
53-1003031-02
Liberal bypass selection and liberal dynamic bypass
1
A: When the node protection desired flag is present, PLR goes through the merge point in the
order of next-next-hop (if present, to achieve node protection), next-hop (link protection), hops
after next-next-hop in sequence of traverse, if any are present.
B: When Node protection desired flag is not set, it simply selects the downstream next hops in
sequence of traverse (example: next-hop, next-next-hop and so on).
Bypass LSP qualification:
A: Bypass LSP cannot traverse any link (forward directional) traversed by protected session
from ingress of LSP to PLR.
B: Bypass LSP cannot traverses any link attached to nodes traversed by protected session
between PLR and egress of LSP.
When there are more than the one bypass LSP qualified to serve for backup path, select the ones
with lowest LSP cost, if the metric is considered. When there are more than one bypass LSP
available with the lowest cost, it selects the one with the lowest number of riding backup sessions.
Liberal bypass selection and liberal dynamic bypass
New facility backup computation mode applies an algorithm between an extremely conservative
approach and an extremely liberal approach. The changes affect how the bypass LSP is qualified.
There are no changes regarding the merge point selection or capability to disable providing node
protection or tie breaker from multiple qualified bypass LSPs and how a dynamic bypass LSP path
is chosen while creating a dynamic bypass.
For a bypass LSP to qualify for the backup path, it must pass following tests:
• Bypass LSP cannot traverse any forward direction links used by protected session.
• While the Liberal Bypass option is enabled, the bypass LSP cannot traverse any nodes
between PLR and MP.
• Bypass LSP cannot reach MP where protected LSP is already in a repaired state.
• Bypass can traverse the nodes between MP and Egress.
• Bypass LSP cannot traverse the locally protected link (this is implicit because the bypass LSP is
already avoided using protected interface).
In summary, all Bypass selection constraints remain same as per existing bypass selection except
that the Bypass can traverse the nodes between the Protected LSP Merge Point and Egress.