Maintenance Description
9-38 Issue 8.0 July 2002
At node 0, the following occurs:
â– The west OC48 RCVR (A/D) circuit pack receives the switch confirmation
and notifies the LNCTL circuit pack.
â– The LNCTL circuit pack transmits a protection switch request to the board
controller on all the circuit packs.
â– The low-speed interface circuit packs that add/drop traffic to/from the
failure, and the west OC48 TRMTR (A/D) and OC48 RCVR (A/D) circuit
packs switch traffic to the protection STS-3 tributaries of OC-48 high-speed
line 1W. An add/drop cross-connection is established between the affected
low-speed interface slot and the protection STS-3 tributaries of OC-48
high-speed line 1W. The add/drop cross-connection is established using
the A bus between the affected low-speed interface circuit pack and the
west OC48 TRMTR (A/D) and OC48 RCVR (A/D) circuit packs. Figure 9-7
shows low-speed interface slot 4A cross-connected to the protection
STS-3 tributary 14 of OC-48 high-speed line 1E.
â– The west OC48 TRMTR (A/D) and OC48 RCVR (A/D) circuit packs loop
back all the through STS-3 tributaries transmitted toward the failure from
the service STS-3 tributaries to the protection STS-3 tributaries of OC-48
high-speed line 1W. The loopback is established using the B bus between
the west OC48 TRMTR (A/D) and OC48 RCVR (A/D) circuit packs.
Figure 9-7 shows extra traffic is preempted and service STS-3 tributary 3 of
OC-48 high-speed line 1W is looped back to protection STS-3 tributary 11.
(Table 9-4 shows the mapping between the service STS-3 tributaries and
their protection STS-3 tributaries.)
In order to prevent misconnections during single node or multiple ring failures, the
FT-2000 OC-48 Add/Drop-Rings Terminal squelches all traffic that cannot be
terminated.
Figure 9-8 shows a 4-node ring with multiple ring failures that isolate node 1 and
cause traffic that cannot be terminated to be squelched. Nodes 0 and 2 perform a
2-fiber ring protection switch and squelch traffic originating from or terminating at
node 1 to prevent any misconnections. Squelching is done by inserting STS-1
path AIS on the protection tributaries that carry traffic terminating at or originating
from node 1. The STS-1 path AIS is returned to the node(s) sending traffic to node
1. At these node(s), the STS-1 path AIS or DS3 AIS is sent to the cross-connect
panels (or equivalent). If nodes 0 and 2 originate or terminate any traffic, STS-1
path AIS or DS3 AIS is also inserted and sent to the local cross-connect panels
(or equivalent).
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