VeEX MPA User Manual page 379

MPA_e_manual_D07-00-129P_RevA00
Protocol Tabs
What Causes an AIS Alarm?
An Alarm Indication Signal (AIS) is an alarm sent to downstream network elements
(NE). It indicates that a defect has been reported by an upstream NE. If an NE has an
alarm condition, such as a Loss of Signal (LOS), Loss of Frame (LOF), or Loss of
Pointer (LOP), it generates an AIS to alert downstream NEs of an upstream failure.
The MPA supports the detection and transmission of Line AIS (AIS-L) and STS Path
AIS (AIS-P) alarms.
An AIS-L is an AIS generated by Section terminating equipment (STE) to alert
downstream Line terminating equipment (LTE) that a defect has been detected on the
incoming SONET Section signal. An STE generates an AIS-L downstream within 125
milliseconds of detecting an LOS or LOF alarm on the incoming SONET signal.
An AIS-P is an AIS generated by an LTE to alert downstream STS Path terminating
equipment (PTE) that a defect, such as an LOP, has been detected on the incoming
SONET Line signal. An LTE declares an AIS-P downstream within 125 milliseconds of
detecting an LOP alarm on the incoming SONET signal.
If the MPA receives an AIS-L or AIS-P alarm, it is reported by the MPA's LEDs and
logged to the Results screen.
The MPA can be used to simulate AIS alarms to verify if downstream NEs react
accordingly to an incoming AIS alarm.
Related Topics:
Unit reports Loss of Signal (LOS)
What causes a B1 error?
What causes a B2 error?
What causes a B3 error?
What causes an AIS alarm?
What causes an RDI alarm?
How to Insert Errors
How to Insert Alarms
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