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Cisco ONS 15600 SDH Reference Manual, Release 9.0
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Chapter 7 Circuits and Tunnels
7.7 Protection Channel Access Circuits
Figure 7-4
Viewing SNCP Switch Counts
In network view, you can right-click on a span and choose the Circuits command to open the Circuits on
Span dialog box. Use the Circuits on Span dialog box to view circuit span usage information and, for
SNCP spans, to perform span switches and lockouts.
7.7 Protection Channel Access Circuits
You can provision circuits to carry traffic on MS-SPRing protection channels when conditions are
fault-free and set up MS-SPRing diagnostic test circuits. Traffic routed on MS-SPRing 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 STM-16 MS-SPRing, STMs 9 to 16 can carry extra traffic when no ring switches are active,
but PCA circuits on these STMs 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
MS-SPRing is provisioned as revertive, this occurs automatically after the fault conditions are cleared
and the reversion timer has expired.
Traffic provisioning on MS-SPRing 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 15600 SDH Procedure Guide
for more information. When
provisioning PCA circuits, two considerations are important to keep in mind:
•
If MS-SPRings are provisioned as nonrevertive, PCA circuits are not restored automatically after a
ring or span switch. You must switch the MS-SPRing manually.
•
PCA circuits are routed on working channels when you upgrade a MS-SPRing from one optical
speed to a higher optical speed. For example, if you upgrade a two-fiber STM-16 MS-SPRing to an
STM-64, STMs 9 to 16 on the STM-16 MS-SPRing become working channels on the STM-64
MS-SPRing.
