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Cisco ONS 15454 Reference Manual, R8.5.x
78-18106-01
Chapter 12 SONET Topologies and Upgrades
12.3 Path Protection
The path protection circuit limit is the sum of the optical bandwidth containing 84 section data
communication channels (SDCCs) or 28 line data communication channels (LDCCs), divided by two if
you are using redundant TCC2/TCC2P cards. The spans can be of any bandwidth from OC-3 to OC-192.
The circuits can be of any size from VT1.5 to 192c.
Figure 12-13 shows a basic four-node path protection configuration. If Node ID 0 sends a signal to Node
ID 2, the working signal travels on the working traffic path through Node ID 1. The same signal is also
sent on the protect traffic path through Node ID 3.
Figure 12-13 Basic Four-Node Path Protection
If a fiber break occurs (Figure 12-14), Node ID 2 switches its active receiver to the protect signal coming
through Node ID 3.
Because each traffic path is transported around the entire ring, path protection configurations are best
suited for networks where traffic concentrates at one or two locations and is not widely distributed. Path
protection capacity is equal to its bit rate. Services can originate and terminate on the same path
protection, or they can be passed to an adjacent access or interoffice ring for transport to the
service-terminating location.
ONS 15454
Node ID 0
ONS 15454
Node ID 1
ONS 15454
Node ID 2
ONS 15454
Node ID 3
32148
= Fiber 1
= Fiber 2