Maintenance Description
Issue 8.0 July 2002
9-39
Figure 9-8. Bidirectional Line-Switched 2-Fiber Ring (Multiple Failures)
Nodes 0 and 2 do not squelch traffic that passes through node 1. Squelching is
only done by nodes that have an active 2-fiber ring protection switch. An isolated
node does not perform a 2-fiber ring protection switch; thus an isolated node does
not squelch.
If any FT-2000 OC-48 Add/Drop-Rings Terminals in the 2-fiber ring are equipped
to provide extra traffic, a 2-fiber ring protection switch will preempt extra traffic.
This applies to the secondary circuit of a DRIP circuit as well, which is carried on
protection capacity, and hence treated as being extra traffic. The secondary circuit
is the combination of the continue segment of the drop and continue (from the
primary node to the secondary node), along with the duplicate segment from the
other ring (from the secondary node to the primary node).
An exception to this occurs during isolation of the primary node of a DRIP circuit.
In a DRIP circuit without failures, the secondary node of the DRIP circuit:
— Adds traffic to a protection tributary on the span towards the primary
node, and
Node 0
1W 1E
1A 2B 8B
1
OC-48
5A
14
1
6
Node 1
1W 1E
1A 8B
14
1
14
1
66
Node 3
1E 1W
1A 8B
1
OC-48
14
1
Node 2
1E 1W
1A 8B
14
1
14
1
6
OC-48OC-48
4A
16
16 16 16
16 16 16 16
3 3 3
3
3A
2A 4B
14
1111 1111
11
14
11
Fiber Cut
STS-1
Path AIS
STS-1
Path AIS
Fiber
Cut
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