Use this procedure to request the local MEP to begin a proactive Delay Measurement session for a particular Class of Service. The results are minimum, maximum, and average, near end and far end, Delay and Delay Variation per 15 minute and 24 hour intervals, reported via SNMP.

When remote “mc” is configured, the class 1 multicast address for the MEP’s level is used. This is useful in a network where the peer MEP's address isn't known or may change, however care must be taken that only one MEP will respond.

Round-trip (RT) delay is measured by sending timestamped DMM frames to the remote end which returns the timestamp, with its own Rx and Tx timestamps, to the originating node in DMR frames where they are again timestamped on receipt. The difference between the local timestamps is the RT delay and, using the remote timestamps, excludes the time it takes the responder to reflect the message. Because the differences, gross RT delay and responder latency, are made from timestamps taken from the same clock (local and remote, respectively) there is no need for synchronization of the clocks at each end.

One-way delay measurements are made using the same timestamped DMM/DMR messages as for RT delay. When the clocks at each end are TOD-synchronized, then the difference between the local Tx and remote Rx timestamps, and the difference between the remote Tx and local Rx timestamps, gives accurate far-end and near-end one-way delay, respectively.

One-way Delay Variation is calculated regardless of clock synchronization between peers, by taking differences between neighboring "one-way delay" measurements. These differences cancel the effect of non-synchronization.

Proactive results are only available by SNMP. The minimum, average, and maximum round-trip, and one-way delay variation per direction, are retrievable. A TCA is configurable for Average and Maximum Round-trip Delay and One-way Delay Variation. The thresholds are user configurable. See Proactive DM Threshold parameters.

When ethoam pm is enabled on a load-sharing LAG, a DM session by default measures delay on the lowest numbered member port. If that member port fails, the session switches to the good member port, and back again when recovered.

Refer to the following restrictions:

• Ethernet OAM pm (ethoam pm) must be enabled. See Procedure 16-4.1: Enable Ethernet OAM Performance Monitoring (PM).

• Proactive DM can be configured on only one Up-MEP for a particular VID, MD level, and priority, and on only one Down-MEP for a particular VID, MD level, priority and port (and only on a port which has ethoam pm enabled).

• Proactive DM is not availabe for MEPs with no VLAN (VID = 0).

• You cannot configure a proactive or on-demand DM session on both an Up and Down MEP having the same VID, MD level, and priority.

• A DM responder may be configured simultaneously with either proactive or on-demand DM, but it must be on the same MEP.

• The “fs-value” can be no greater than the mtu size configured for the port where the MEP is configured (see show interface ethernet Max Frame Size).

• 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).

• A configured responder is necessary to support a remote DM session (Proactive or On-Demand) when there is not a DM session for the same VLAN, CoS and MD level (and port, for a Down-MEP) enabled on the MEP.

• For valid one-way delay measurement data, the system clocks at the local MEP and remote MEP must be TOD-synchronized. Otherwise, the one-way delay measurements are invalid that may result in random threshold crossing or clearing.