Protection Channel Access Circuits; Blsr Sts And Vt Squelch Tables; Blsr Sts Squelch Table - Cisco ONS 15600 Reference Manual

Chapter 7 Circuits and Tunnels

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. If BLSRs are
provisioned as nonrevertive, PCA circuits are not restored automatically after a ring or span switch. You
must switch the BLSR manually.

7.8 BLSR STS and VT Squelch Tables

If a ONS 15600 is on a network with ONS 15454 nodes, it is possible to display STS and VT squelch
tables on the ONS 15454 nodes depending on the type of circuits created. For example, if a fiber cut
occurs, the BLSR squelch tables show STSs or VTs that will be squelched for every isolated node.
Squelching replaces traffic by inserting the appropriate alarm indication signal path (AIS-P) and
prevents traffic misconnections. For an STS with a VT-access check mark, the AIS-P will be removed
after 100 ms. To view the squelch tables, refer to the "Manage Circuits" chapter in the
Cisco ONS 15454 Procedure Guide for detailed instructions. For more information about BLSR
squelching, refer to Telcordia GR-1230.

7.8.1 BLSR STS Squelch Table

BLSR STS squelch tables show STSs that will be squelched for every isolated node.
The BLSR Squelch Table window displays the following information:
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STS Number—Shows the BLSR STS numbers. For two-fiber BLSRs, the number of STSs is half
the BLSR OC-N, for example, an OC-48 BLSR squelch table will show 24 STSs. For four-fiber
BLSRs, the number of STSs in the table is the same as the BLSR OC-N.
West Source—If traffic is received by the node on its west span, the BLSR node ID of the source
appears. (To view the BLSR node IDs for all nodes in the ring, click the Ring Map button.)
West VT (from the West Source) — A check mark indicates that the STS carries incoming VT
traffic. The traffic source is coming from the west side.
West VT (from the West Destination) — A check mark indicates that the STS carries outgoing VT
traffic. The traffic is dropped on the west side.
West Dest—If traffic is sent on the node's west span, the BLSR node ID of the destination appears.
East Source—If traffic is received by the node on its east span, the BLSR node ID of the source
appears.
East VT — (from the East Source) - A check mark indicates that the STS carries incoming VT
traffic. The traffic source is coming from the east side.
7.7 Protection Channel Access Circuits
Cisco ONS 15600 Reference Manual, R8.0
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