Cisco Systems 15454 11.10 BLSR Protection Channel Access Circuits

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Cisco ONS 15454 Reference Manual, R7.0
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Chapter 11 Circuits and Tunnels
11.10 11.10 BLSR Protection Channel Access Circuits
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:
• If BLSRs are provisioned as nonrevertive, PCA circuits are not restored automatically after a ring
or span switch. You must switch the BLSR manually.
• PCA circuits are routed on working channels when you upgrade a BLSR from a two-fiber to a
four-fiber or from one optical speed to a higher optical speed. For example, if you upgrade a
two-fiber OC-48 BLSR to an OC-192, STSs 25 to 48 on the OC-48 BLSR become working channels
on the OC-192 BLSR.
Node B
Go and Return working connection
Go and Return protecting connection
Node A
96953
Any network Any network