Restrictions for Alarms
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In T3, an AIS alarm is supported only in the framed mode and not supported in the unframed mode.
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This chapter provides information about alarms supported for SONET and SDH, and their maintenance.
Alarms are triggered when a component fails or does not perform as expected. Alarms are triggered by the chassis.
Alarms can be defined using the following two terms:
Alarm State—It is the state the chassis enters when a certain event occurs. For example, the state of the chassis when the ambient temperature is beyond the specified limits.
Alarm Indication—It is a visual signal to indicate the alarm state. For example, the TEMP LED glows red if the ambient temperature is beyond the specified limits, and it turns green if the ambient temperature is within specified limits.
Typically, a failure condition detected by a chassis results in one or more error conditions sent both upstream and downstream on the network.
Alarm Indication Signal (AIS)—AIS alarms are reported downstream from a detecting device, and to prevent consequential downstream failures or alarms from being raised.
Remote Defect Indicator (RDI)—RDI alarms are always reported upstream from the detecting device.
Note |
Even when the controller is in the down state with alarms, the cross connection between the controllers is up. |
In T3, an AIS alarm is supported only in the framed mode and not supported in the unframed mode.
SONET equipment detects events and alarms at each of the three layers — section, line and path. A SONET chassis sends alarms in both upstream and downstream directions in order to notify other devices of the problem condition.
The interface of an active alarm or defect is maintained in a down/down state. The process used to troubleshoot down/down SONET interfaces is similar to that of digital interfaces, such as T1 and T3.
The following table lists the types and sub types of SONET Alarms.
Alarm Type |
Sub Alarm Type |
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Section Alarms |
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Line Alarms |
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Path Alarms |
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VT Alarms |
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T1 Alarms |
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T3 Alarms |
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The following table lists the types and sub types of SDH Alarms.
Alarm Type |
Sub Alarm Type |
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Section Alarms |
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Line Alarms |
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STS Path Alarms |
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VT Path Alarms |
|
Note |
TIM alarms are not supported. |