Gmpls Protection And Restoration; 1:1 Lsp Protection; Shared Mesh Restoration And M:n Path Protection - Cisco CRS Configuration Manual

Implementing MPLS Traffic Engineering
• Protection and restoration
Related Topics
Configuring Router IDs, on page 242
Configuring OSPF over IPCC, on page 244

GMPLS Protection and Restoration

GMPLS provides protection against failed channels (or links) between two adjacent nodes (span protection)
and end-to-end dedicated protection (path protection). After the route is computed, signaling to establish the
backup paths is carried out through RSVP-TE or CR-LDP. For span protection, 1+1 or M:N protection schemes
are provided by establishing secondary paths through the network. In addition, you can use signaling messages
to switch from the failed primary path to the secondary path.
Only 1:1 end-to-end path protection is supported.
Note
The restoration of a failed path refers to the dynamic establishment of a backup path. This process requires
the dynamic allocation of resources and route calculation. The following restoration methods are described:
• Line restoration—Finds an alternate route at an intermediate node.
• Path restoration—Initiates at the source node to route around a failed path within the path for a specific
LSP.
Restoration schemes provide more bandwidth usage, because they do not preallocate any resource for an LSP.
GMPLS combines MPLS-FRR and other types of protection, such as SONET/SDH and wavelength.
In addition to SONET alarms in POS links, protection and restoration is also triggered by bidirectional
forwarding detection (BFD).

1:1 LSP Protection

When one specific protecting LSP or span protects one specific working LSP or span, 1:1 protection scheme
occurs. However, normal traffic is transmitted only over one LSP at a time for working or recovery.
1:1 protection with extra traffic refers to the scheme in which extra traffic is carried over a protecting LSP
when the protecting LSP is not being used for the recovery of normal traffic. For example, the protecting LSP
is in standby mode. When the protecting LSP is required to recover normal traffic from the failed working
LSP, the extra traffic is preempted. Extra traffic is not protected, but it can be restored. Extra traffic is
transported using the protected LSP resources.

Shared Mesh Restoration and M:N Path Protection

Both shared mesh restoration and M:N (1:N is more practical) path protection offers sharing for protection
resources for multiple working LSPs. For 1:N protection, a specific protecting LSP is dedicated to the protection
of up to N working LSPs and spans. Shared mesh is defined as preplanned LSP rerouting, which reduces the
restoration resource requirements by allowing multiple restoration LSPs to be initiated from distinct ingress
nodes to share common resources, such as links and nodes.
Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router, Release 5.1.x
DWDM Transponder Integration
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