Y.1731 service OAM in this release supports:

Loss Measurement (LM)

• Proactive (CCM-based )

• On-Demand (LMM/LMR-based)

• User data counts

• Synthetic (Fast CCM) counts

• Increased precision FLR reporting

Delay Measurement (DM)

• Proactive (DMM/DMR based)

  • Two-way (round trip) Delay Measurement

  • One-way Delay Measurement (Synchronized TOD clock needed)

  • One-way Delay Variation Measurement (no synchronized TOD clock needed)

  On-Demand (DMM/DMR based)

  • Two-way (round trip) Delay Measurement

  • One-way Delay Measurement (Synchronized TOD clock needed)

• Ethernet AIS

• Y.1731/G.8021 CCM alarms

The OAM PM features, LM and DM, can be enabled when CFM is enabled. Parts of the system configuration must be in place on the port(s) or LAG before OAM-PM is enabled, and cannot be changed while OAM-PM is active. Disabling OAM-PM clears all provisioning directly associated with it. The system configuration which must be configured first includes “mode dvlan-tunnel”, spanning tree or ERP participation, LAG membership on the OAM-PM ports, and mtu-size on all ports. In addition, the VLAN participation on a port enabled for OAM-PM cannot be changed if an LM or DM session is configured in that VLAN.

Note:

Protection schemes which replicate broadcast, unlearned unicast, or multicast traffic (call any of these MC) may be incompatible with accurate Y.1731 Loss Measurement (LM) on the VLNC42x.

ERP and RSTP are two examples. If the NE has two (or more) unblocked ports, MC traffic is replicated and sent out each port. The LM Tx counter increments for each replication of monitored frames. However, the remote end receives only one of the replicates. A comparison of LM local Tx and remote Rx counts shows apparent frame loss when none has occurred. Additionally, when the remote end sends MC traffic, the NE with unblocked ports also counts those, because they are passed through.

For example ERP uses two ports. Assume proactive LM is active at MD level 4 and a MEP at MD level 5 has CCM enabled at 1 second intervals. Then, the proactive LM Tx count includes two replicate CCM's generated by the local MEP at level 5 and one pass-through CCM from the remote MEP. The remote MEP receives and counts only one. If this were the only traffic, then the reported FLR would be a constant 67%. In a working network, the degree of inaccuracy depends on the mix of unicast and MC traffic. During times of no MC traffic, the accuracy is 100%.

On-demand LM is similar. Its Tx count includes CCM at the same MD level, in addition to those of levels above.