ITU-T Y.1731 augments IEEE 802.1ag in defining capabilities to perform Performance Monitoring (PM) for Ethernet services. It also provides additional Fault Management (FM) capabilities. Y.1731 defines the frame format and multicast addresses to be used for both PM and FM. The following procedures and packet formats are defined:
AIS (Alarm Indication Signal): Generated when an end-point detects loss of connectivity
Lock: Used to verify connectivity problems in out-of-service mode
Test: Used to test the connectivity out-of-service. It can be used as part of RFC 2544 or ITU-T Y.1564 testing
Delay Measurements: Using DMM/DMR procedure
Loss Measurement: Using LMM/LMR procedure
Some messages use unicast MAC DA and some use reserved multicast DA, which is treated as L2CP. For multicast, the MAC DA address is defined as follows:
There are two types of frames: Class 1 and Class 2
Class 1 - used by CCM - uses MAC DA of 01-c2-80-00-00-30 through 01-c2-80-00-00-3x, where MEG level is represented by x
Class 2 - used by LBM and LTM - uses MAC DA of 01-c2-80-00-00-3y through 01-c2-80-00-00-3F, where y=8+MEG level