Use this procedure to request a MEP to begin a local on-demand Loss Measurement session for a particular Class of Service (CoS). A single measurement is made, which can be deferred using a start time. The results are retrievable via show on-demand-lm-stats. When remote mc is configured, the class 1 multicast address for the MEP’s level is used.

The on-demand loss measurement provides a troubleshooting tool by CLI. It consists of frame loss ratio (FLR) measured over a specified interval at a specified time. On-demand results per direction are reported at the end of the configured measurement interval.

On-Demand LM may be conducted on a MEP running Proactive LM, even for the same CoS.

On-Demand LM may be enabled on a MEP regardless if CCM is enabled.

A single measurement is made for an On-Demand session, which can be deferred using a start time. The measurement consists of a pair of Loss Measurement Messages (LMM) and the received Loss Measurement Replies (LMR) from which the count differences gives the number of frames sent and received during the period between them. That period is configurable from 1 second up to 10 minutes.

Refer to the following restrictions:

• On-demand LM is available only when ethoam pm is enabled.

• On-demand LM can be configured on only one Up-MEP for a particular VID and priority, and on only one Down-MEP for a particular VID and priority and port (and only on a port which has ethoam pm enabled). You cannot enable an on-demand LM session on both an Up and Down MEP having the same VID and priority.

• You can enable on-demand LM simultaneously with an on-demand LM responder and proactive LM, for the same VID and priority, but they must all be on the same MEP.

• The command is rejected if remoteMEPID is specified, but the remote MEP MAC address is not known (CCM are not received from the remote MEP).

• You should not use the multicast address when there is a possibility of more than one reply.

• The remote peer MEP should also have either an overlapping on-demand LM session or an LM responder enabled.

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.