Cisco Systems ONS 15600 Protection Channel Access Circuits, Viewing Path Protection Switch Counts

Chapter 7 Circuits and Tunnels

7.7 Protection Channel Access Circuits

Figure 7-5 Viewing Path Protection Switch Counts

If ONS 15600s are connected to a third-party network, you can create an open-ended path protection circuit to route a circuit through it. To do this, you create three circuits. One circuit is created on the source ONS 15600 network. This circuit has one source and two destinations, one at each ONS 15600 that is connected to the third-party network. The second circuit is created on the third-party network so that the circuit travels across the network on two paths to the ONS 15600s. That circuit routes the two circuit signals across the network to ONS 15600s that are connected to the network on other side. At the destination node network, the third circuit is created with two sources, one at each node connected to the third-party network. A selector at the destination node chooses between the two signals that arrive at the node, similar to a regular path protection circuit.

7.7 Protection Channel Access Circuits

You can provision circuits to carry traffic on BLSR protection channels when conditions are fault-free and set up BLSR diagnostic test circuits. 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 resolved 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 on the circuit creation wizard. Refer to the Cisco ONS 15600 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.

Cisco ONS 15600 Reference Manual, R7.2

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