Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) User Manual
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Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide
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MPLS Fast Reroute using facility backup over a bypass LSP
1
MPLS Fast Reroute using facility backup over a bypass LSP
A bypass LSP is an MPLS LSP that serves as a tunnel to support facility backup of multiple, Fast
Reroute LSPs, as specified in RFC 4090. Although the underlying mechanism of this feature is
facility backup, the execution of facility backup is implemented through a user-defined bypass LSP,
so this section focuses on bypass LSP.
The advantage to using bypass LSP is an improvement in the scalability of protection. It provides a
nearly hitless backup and, as a result, improves network resiliency. A bypass LSP consists of a
predefined tunnel with a list of LSPs for which it is always ready to reroute traffic and is, therefore,
a many-to-one backup. (With a detour backup, as described in
“MPLS fast reroute using one-to-one
, the network calculates an end-to-end detour for each disrupted LSP.)
The following definitions are important for understanding and configuring bypass LSPs:
•
Protected LSP: An LSP whose traffic is carried over the bypass LSP when a link or router fails
along the path of the protected LSP. When an MPLS LSP is configured to have Fast Reroute
backup, that LSP can also be configured to request either facility backup or one-to-one backup.
•
Facility backup: The standards-based mechanism for many-to-one backup.
•
Bypass LSP: A tunnel that carries traffic when any number of its protected LSPs fail.
•
Point of local repair (PLR): A router where the protected LSP and the bypass LSP first intersect
and the LSPs bypass protection begins. Put another way, the PLR is the ingress of the bypass
LSP. The PLR can be the ingress of the protected LSP or a transit node of the protected LSP.
(refer to PLR/R2 in
•
Merge point (MP): The egress router of the bypass LSP, where it merges the traffic back into
the protected LSPs. (R4 in
is the MP.) At the MP, the protected LSPs continue to carry
traffic towards their own egress routers. Just as the PLR is common to all the LSPs protected by
a specific bypass LSP, the MP must also be common to the protected LSPs.
•
Exclude interface: An MPLS interface that is either a physical interface or a LAG and has the
following traits:
•
It is an interface on the path of the protected LSP. (The notion that an excluded interface is
protected by a bypass LSP is described in
.)
•
It is an interface that cannot be part of the bypass LSP itself.
•
Exclude interfaces can consist of individual interfaces, ranges of interfaces, groups, or a
LAG.
FIGURE 14
Facility backup applied to multiple routers over a bypass LSP