Selecting 802.1ag enables Continuity Check Messages (CCM), Loopback Message (LBM) and Link
Trace Message (LTM). ITU-T Y.1731 provides all of the 802.1ag functionality with additional
performance monitoring capabilities including Frame Loss (LM) and Delay (DM).
802.1ag/Y.1731 Connectivity Fault Management Functions
802.1ag/Y.1731 Functions supported are as listed:
Fault Detection – Continuity Check:
CCM "heartbeat" messages are transmitted at a configurable periodic interval by MEPs.
Network/Path Discovery – Link trace message:
Equivalent to a "traceroute" test. MIPs and MEPs along the path send a response.
Fault verification and isolation – Loopback:
Verify connectivity to a specific point in the message. Equivalent to "ping" test.
Frame Loss Measurement
Two local counters for each peer MEP:
TxFCf: Counter for in-profile data frames transmitted towards peer MEP
RxFCf: Counter for in-profile data frames received from peer MEP
Single-ended ETH-LM:
On demand OAM
MEP sends LMM frame (Unicast DA or Multicast Class 1 DA) and receives LMR frame (Unicast DA) with counters
CCM frames contain frame counters.
Single Ended Frame Delay Measurement
LMM frames contain frame counters.
Delay Measurement
On demand OAM for measuring Frame Delay (FD) and Frame Delay Variation (FDV):
TxTimeStampf = Timestamp transmission of DMM frame
RxTimef = Reception time of the DMM frame
RxTimeb = Reception of DMR frame
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