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Cisco ONS 15454 Reference Manual, R8.5.x
78-18106-01
Chapter 11 Circuits and Tunnels
11.9.2 Go-and-Return Path Protection Routing
11.9.2 Go-and-Return Path Protection Routing
The go-and-return path protection routing option allows you to route the path protection working path
on one fiber pair and the protect path on a separate fiber pair (Figure 11-8). The working path will always
be the shortest path. If a fault occurs, both the working and protection fibers are not affected. This feature
only applies to bidirectional path protection circuits. The go-and-return option appears in the Circuit
Attributes panel of the Circuit Creation wizard.
Figure 11-8 Path Protection Go-and-Return Routing
11.10 BLSR Protection Channel Access Circuits
You can provision circuits to carry traffic on BLSR protection channels when conditions are fault-free.
Traffic routed on BLSR PCA circuits, called extra traffic, has lower priority than the traffic on the
working channels and has no means for protection. During ring or span switches, PCA circuits are
preempted and squelched. For example, in a two-fiber OC-48 BLSR, STSs 25 to 48 can carry extra traffic
when no ring switches are active, but PCA circuits on these STSs are preempted when a ring switch
occurs. When the conditions that caused the ring switch are remedied and the ring switch is removed,
PCA circuits are restored. If the BLSR is provisioned as revertive, this occurs automatically after the
fault conditions are cleared and the reversion timer has expired.
Traffic provisioning on BLSR protection channels is performed during circuit provisioning. The
Protection Channel Access check box appears whenever Fully Protected Path is unchecked in the circuit
creation wizard. Refer to the Cisco ONS 15454 Procedure Guide for more information. When
provisioning PCA circuits, two considerations are important to keep in mind:
Node B
Go and Return working connection
Go and Return protecting connection
Node A
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