General detection, processing and reaction

All Facility MEPs that support CCM functions must only have one remote MEP peer. Facilities MEPs validate point-to-point logical or physical Ethernet transports. Configure service MEPs if multipoint-service validation is required.

There are three distinct functions for a Facility MEP:

• general detection

  This determines that a fault has occurred. In this case, the MEP performs its normal functions such as: recognizing the fault condition, maintaining the local errors and reporting based on low-priority-setting, and taking no further action. This is the default.

• fault processing

  By default, there is no action taken as a result of a MEP state machine transition beyond alarming. To take action which may include a SAP operational state change, generation of AIS, or fault propagation and mapping, the appropriate facility fault configuration parameter must be configured and enabled. The general reaction to a fault is described below. More details are including the section describing the functions of the individual facility MEPs.

  • port

    This affects link operational status of the port. Facility failure changes the operational state to Link Up. This indicates that the port has been brought down as a result of OAM MEP Fault. This operational state has the equivalent function to port down condition.

  • LAG

    This affects link operational status of the LAG. Facility failure changes the operational state of the LAG to DOWN. This indicates that the LAG has be brought down as a result of OAM MEP Fault.

  • tunnel MEP

    This enters faulty state and further impacts the operational state of the SAPs linked to the tunnel MEP state.

    • Epipe SAP remains operationally up, SAP's flag set to OamTunnelMEPFault

    • Ipipe SAP remains operationally up, SAP's flag set to OamTunnelMEPFault

    • VPLS, IES and VPLS SAPs transition to operationally down, the SAP's flag is set to OamTunnelMEPFault. SAP operational states and flags are affected only by the tunnel-fault configuration option.

  • router IP interface

    This affects operational status of the IP Interface.

• propagation

  Services appropriately linked to the Facility MEP take the following service-specific actions:

  • Epipe generates AIS or use Fault Propagation and OAM mappings.

  • VPLS does not propagate fault using AIS unless service-based MEPs are configured and contain MEP-specific AIS configuration. SAP transitions occur when the facility MEP failure is recognized by the service.

  • IES and VPRN, as Layer 3 functions, act as boundaries for Layer 2 fault processing. No propagation functions occur beyond what is currently available as part of fault propagation: SAP down.

• AIS-enable configuration options

  Epipe services support the ais-enable configuration option under the SAP hierarchy level. This structure, outside of the MEP context, creates a special link between the Epipe service SAP and the facility MEP. If a facility MEP enters a fault state, all Epipe service SAPs with this configuration generate lowest-level AIS at the level configured under the facility MEP. As with fault propagation, AIS generation is restricted to Epipe services only. The actions taken by the other services are described in more detail in the relevant facility MEP sections.

  Note: Facility MEPs do not support the generation of AIS to an explicitly configured endpoint. An explicitly configured endpoint abstracts multiple endpoints within its context; for example, pseudowire (PW) redundancy. Although the linkage of a facility MEP to an Epipe, and AIS generation triggered as a result of the facility MEP failure can be configured, AIS generation is not supported and is unpredictable. When an explicit endpoint is configured, service-based MEPs are required when AIS generation is the needed behavior.