User Manual UMN:CLIV8102185MEG LevelEight MEG levels are available to accommodate different network deployment scenarios.There are two cases based upon ETH layer encapsulation:• Shared MEG Levels: Customer, provider, and operator share the MEG levels.- Customer role: Level 7, 6, 5- Provider role: Level 4, 3- Operator role: Level 2, 1• Independent MEG Levels: Customer and provider do not share the MEG levels butprovider and operator share the MEG levels.- Provider bridge: C-Tag, S-TagFig. 7.3 Shared MEG LevelsY.1731 Functions for Fault managementITU-T Y.1731 OAM supports the following functions for fault management:• Ethernet Continuity Check (ETH-CC)Each MEP sends periodic CCMs to other MEPs with a multicast destination address.The loss of CCMs that ride along the data path would indicate a connectivity failure.• Ethernet Loopback (ETH-LB)A LBM is sent to a unicast destination MAC address. MEP at the destination MACaddress responds to the LBM with an LBR. These messages are useful for verifyingconnectivity with a specific L2 destination.• Ethernet Link Trace (ETH-LT)ETH-LT function is used to retrieve adjacency relationship between a MEP and aremote MEP or MIP.• Ethernet Alarm Indication Signal (ETH-AIS)ETH-AIS is used to suppress alarms at the client layer following detection of defectconditions at the server layer. Upon detecting a defect condition, the MEP starttransmitting periodic AIS frames at a configured client MEG level.• Ethernet Locked Signal (ETH-LCK)ETH-LCK is used to communicate the administrative locking of a server layer MEPand consequential interruption of data traffic forwarding towards the MEP expectingthe traffic.
