When CFM is the OAM module at the other end, it is required to use any of the following methods (depending on local configuration) to notify the remote peer:
generating AIS for specific MEP levels
sending CCM with interface status TLV ‟down”
stopping CCM transmission
For using AIS for fault propagation, AIS must be enabled for the MEP. The AIS configuration needs to be updated to support the MD level of the MEP (currently it only supports the levels above the local MD level).
Note that the existing AIS procedure still applies even when fault propagation is disabled for the service or the MEP. For example, when a MEP loses connectivity to a configured remote MEP, it generates AIS if it is enabled. The new procedure that is defined in this document introduces a new fault condition for AIS generation, fault propagated from SMGR, that is used when fault propagation is enabled for the service and the MEP.
The transmission of CCM with interface status TLV is triggered and does not wait for the expiration of the remaining CCM interval transmission. This rule applies to CFM fault notification for all services.
For a specific SAP and SDP-binding, CFM and SMGR can only propagate one single fault to each other for each direction (up or down).
When there are multiple MEPs (at different levels) on a single SAP and SDP-binding, the fault reported from CFM to SMGR is the logical OR of results from all MEPs. Basically, the first fault from any MEP is reported, and the fault is not cleared as long as there is a fault in any local MEP on the SAP and SDP-binding.