Specifications

Reference Guide
7-27
WAN Card WAN Card User Screens and Settings
The WAN links between the Device and the System Unit (A, B, A1, and B1) are called
tributaries
. The WAN link between the two SYS Units (C and C1) is referred to as a
trunk
.
In the normal condition (no WAN groups selected), a failure on any of the tributaries supplying
Device 1 would be reported at SYS 1 and Device 1 only. A failure of the trunk from C to C1
would be reported at SYS 1 and 2 only.
When Groups are created at both system units, a trunk failure (C to C1) will inform all of the
associated tributaries (A and B, A1 and B1) of that condition.
When groups are used in conjunction with the Network Management option (mentioned
earlier) and the AIS/ALM is set to
tcodr
, a failure of any of the tributaries will propagate the
failure through the trunk to the associated tributary at the other end (A to A1 or B to B1).
The following notification procedure is followed:
1. A Loss of Signal, Loss of Frame, Error Rate Exceeded, or AIS failure of the transmit
leg of W1-1(A) occurs between Device 1 and SYS 1.
2. SYS 1 detects the failure on the receive leg and declares an alarm for W1-1(A).
3. SYS 1 sets the A Bit (Yellow Alarm) in the transmit leg of W1-1(A). Device 1 detects
this condition and knows not to use W1-1(A).
4. SYS 1(C) sends an alarm message to SYS 2 (C1), telling it that W1-1(A) is either in a
CGA_RED or AIS alarm.
5. SYS 2 sets the transmit leg of W3-1(A1) into AIS (CGA_RED). Device 2 detects this
condition and knows not to use W3-1(A1).
When the original failure is corrected, the alarm is also cleared for downstream tributaries.