Mapping of CCM Defects to APS Events
The continuity check message (CCM) engine marks the status of working and protected transport entities as either Down, Degraded, or Up.
Down—The monitored path is declared down if any of the following Multiple End Point (MEP) defects occur:
RDI indicating signal failure
Degraded—The monitored path is declared degraded if any of the following MEP defects occur:
Up—The monitored path is declared up in the absence of any of the above events.
As show in Figure 1, the APS event generator generates the following APS events based on the status of the working and protection paths:
SF—Signal failure on working path
RSF—Working path recovers from signal failure
SF-P—Signal failure on protection path
RSF-P—Protection path recovers from signal failure