Example Applications
Page 424 7450 ESS MPLS Guide
The objective of this application is to ensure optical network path diversity for primary/backup
paths of an overlay IP network. It thus aims to resolve situations where the UNI-C router has no
topological visibility of the optical network, and to allow the router to indicate that paths have to
be either co-routed or avoid specific optical nodes or links along a path.
Route diversity for LSPs from single homed UNI-C router and dual-homed UNI-C router is a
common requirement in optical transport networks. Dual homing is typically used to avoid a single
point of failure (for example, the UNI link or OXC) or to allow two disjoint connections to form a
protection group.
For the dual-homing case, it is possible to establish two connections from the source router to the
same destination router where one connection is using one UNI link to, for example, OXC1 and
the other connection is using the UNI link to OXC2. In order to avoid single points of failure
within the optical network, it is necessary to also ensure path (gLSP) diversity within the provider
network in order to achieve end-to-end diversity for the two gLSPs between the two routers.
Figure 37: Multi-Layer Resiliency
As the two connections are entering the provider network at different OXC devices, the OXC
device that receives the connection request for the second connection needs to be capable of
determining the additional path computation constraints such that the path of the second LSP is
disjointed with respect to the already established first connection entering the network at a
different PE device.
24853
R2
OXC2
R4
OXC4 OXC6 OXC8
R1
OXC1
R3
OXC3
gLSP2
OXC5 OXC7
UNI
UNI
UNIUNI
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