Figure 80. Squelching On Isolated Node Connection - Alcatel 1850 TSS-320 Technical Handbook

SQUELCHING FUNCTION
The Squelching function is activated when a node that carries Drop/Insert streams, remains isolated
because of a double failure.
In this case to avoid misconnections on the AU4 involved in MS SPRING protection, an AIS signal will
be inserted on Low Priority streams transmitted from the nodes adjacent to the isolated one. See Figure
80.
Before Node 2 isolation because of the double failure, the following connections were active using the
AU4#1
– Stream between Port 3 and Port 1
– Stream between Port 2 and Port 4
After a second failure, the Nodes adjacent to the isolated Node 2 send AIS on the Low Priority traffic
(AU4#9) by means of the Squelching function thus avoiding the misconnection between Port 3 and Port 4.
If the Squelch function were not active, the MS SPRING algorithm would activate the Bridge and Switch
functions on the nodes adjacent to Node 2 thus misconnecting Port 3 and Port 4 using AU4#9 as
protection. In virtue of squelching function the nodes adjacent to isolated Node 2 send AIS on Low Priority
AU4#9 avoiding in this way the misconnection between Port 3 and Port 4 in this case.
After the failure has been removed, a similar reverse sequence of operations on the NEs adjacent to the
recovered span will be activated. The reverse procedure can start after a step programmable WTR.
PORT 3
AU4 #1
BRIDGE
side A
1
SWITCH
side A
A
B
AIS ON
AU4 # 9
PASS-THROUGH
6
Technical Handbook Common
Functional Description
PORT 1
AU4 #1
B A
(SF/
AIS ON
AU4 # 9
AIS ON
AU4 # 9
PASS-THROUGH
A B
WORKING CHANNELS
PROTECTION CHANNELS

Figure 80. Squelching on isolated Node connection

PORT 2
AU4 #1 AU4 #1
B
2
(SF/
5
A B
8DG 07734 AAAA Edition 01
PORT 4
A
SWITCH
side B
3
BRIDGE
side B
B
4
AIS ON
A AU4# 9
AIS ON
AU4 # 9
PASS-THROUGH
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