3Com CoreBuilder 9000 User Manual page 207

Table 27 Physical Layer Statistics (continued)
Statistic
SONET path alarm indication signal state (Path AIS)
SONET line alarm indication signal state (Line AIS)
SONET line remote defect indication state (Line RDI)
SONET path remote defect indication state (Path RDI)
Description
The AIS is an all-ONES characteristic or adapted information
signal. It is generated to replace the normal traffic signal
when it contains a defect condition in order to prevent
consequential downstream failures being declared or alarms
being raised.
AIS can also be identified as:
- AIS-L (Line Alarm Indication Signal)
- SP-AIS (STS Path Alarm Indication Signal)
- VP-AIS (VT Path Alarm Indication Signal)
A signal returned to the transmitting Terminating Equipment
upon detecting a Loss of Signal, Loss of Frame, or AIS defect.
RDI was previously known as FERF.
RDI can also be identified as:
- RDI-L (Line Remote Defect Indication)
- RDI-P (STS Path Remote Defect Indication)
- RDI-V (VT Path Remote Defect Indication)
Physical Layer Statistics 207