Continuity Check (CC)

A Continuity Check Message (CCM) is a multicast frame that is generated by a MEP and multicast to all other MEPs in the same MA. The CCM does not require a reply message. To identify faults, the receiving MEP maintains an internal list of remote MEPs it should be receiving CCM messages from.

This list is based on the remote MEP ID configuration within the association the MEP is created in. When the local MEP does not receive a CCM from one of the configured remote MEPs within a preconfigured period, the local MEP raises an alarm.

The following figure shows a CFM continuity check.

Figure: CFM Continuity Check

The following figure shows a CFM CC failure scenario.

Figure: CFM CC failure scenario

The following functions are supported:

• CC can be enabled and disabled for an MEP.

• MEP entries can be configured and deleted in the CC MEP monitoring database manually. Only remote MEPs must be configured. Local MEPs are automatically added to the database when they are created.

• The CCM transmit interval is configurable. See the Diagnostics command reference for more information about supported timer intervals on different platforms for MEPs used in the service context and G.8032 control instance context.

• CCM will declare a fault, when:

  • the CCM stops hearing from one of the remote MEPs for 3.5 times CC interval

  • the CCM hears from a MEP with a LOWER MD level

  • the CCM hears from a MEP that is not part of the local MEP’s MA

  • the CCM hears from a MEP that is in the same MA but not in the configured MEP list

  • the CCM hears from a MEP that is in the same MA with the same MEP ID as the receiving MEP

  • the CC interval of the remote MEP does not match the local configured CC interval

  • the remote MEP is declaring a fault

• An alarm is raised and a trap is sent if the defect is greater than or equal to the configured low-priority-defect value.

• Remote Defect Indication (RDI) is supported but by default is not recognized as a defect condition because the low-priority-defect setting default does not include RDI.

• The Sender ID TLV may optionally be configured to carry the Chassis ID. When configured, the following information will be included in CCM messages:

  • Only the Chassis ID portion of the TLV will be included.

  • The Management Domain and Management Address fields are not supported on transmission.

  • The Sender ID TLV is not supported with subsecond CCM-enabled MEPs.

  • The Sender ID TLV is supported for service (id-permission) MEPs.