The continuity check function is supported by 802.1ag and Y.1731 on the 7705 SAR. A Continuity Check Message (CCM) is a multicast frame that is generated by a MEP and sent to its remote MEPs in the same MA. The CCM does not require a reply message. To identify faults, the receiving MEP maintains a MEP database with the MAC addresses of the remote MEPs with which it expects to maintain connectivity checking. The MEP database can be provisioned manually. If there is no CCM from a monitored remote MEP in a preconfigured period, the local MEP raises an alarm.
Continuity checks are enabled using the eth-cfm>mep>ccm-enable command for Epipe and VPLS services and for router network interfaces.
The following CC capabilities are supported:
enable and disable CC for a MEP
automatically put local MEPs into the database when they are created
manually configure and delete the MEP entries in the CC MEP monitoring database. The only local provisioning required to identify a remote MEP is the remote MEP identifier (using the remote-mepid mep-id command).
CCM transmit interval: 10ms, 100ms, 1s, 10s, 1m, 10m (default: 10s)
transmit interval: 10ms, 100ms, 1s, 10s, 1m, 10m (default: 10s)
CCM declares a fault when it:
stops hearing from one of the remote MEPs for a period of 3.5 times the CC interval
hears from a MEP with a lower MD level
hears from a MEP that is not in the same MA
hears from a MEP that is in the same MA but is not in the configured MEP list
hears from a MEP that is in the same MA with the same MEP ID as the receiving MEP
recognizes that the CC interval of the remote MEP does not match the local configured CC interval
recognizes that the remote MEP declares 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.
CC must be enabled in order for RDI information to be carried in the CCM OAMPDU
The optional ccm-tlv-ignore command can be used to ignore the receipt of interface-status and port-status TLVs in the ETH-CCM PDU on a facility MEP. No processing is performed on ignored ETH-CCM TLV values.
Any TLV that is ignored is reported as absent to the relevant remote peer, and the values in the TLV do not have any effect. This is the same behavior as if the received ETH-CCM PDU never included these TLVs in the first place. If the TLV is not properly formed, the ETH-CCM PDU will fail the packet parsing process, which will cause it to be discarded and an alarm to be raised.