Juniper Networks JUNOS OS 10.4 - Manual (Page 147)

For two-way (round-trip) Ethernet frame delay measurement, either MEP can send a
request to begin a two-way delay measurement to its peer MEP, which responds with
timestamp information. Run-time statistics are collected and displayed at the initiator
MEP. The clocks do not need to be synchronized at the transmitting and receiving MEPs.
The Junos OS supports the optional timestamps in delay measurement reply (DMR)
frames to increase the accuracy of delay calculations. The Junos OS also supports
hardware-assisted timestamping for Ethernet frame delay protocol data units (PDUs)
in the reception path.
Use the show commands at the initiator MEP to display two-way delay statistics, and at
the receiver MEP to display one-way delay statistics.
The following are some limitations with regard to using Ethernet frame delay
measurement:
• This feature is available only on MX Series routers.
• Ethernet frame delay measurements are available only when the distributed periodic
packet management daemon (ppmd) is enabled.
• The statistics collected are lost after graceful Routing Engine switchover (GRES).
• You can monitor only one session to the same remote MEP or MAC address.
• Accuracy is compromised when the system changes (such as from reconfiguration).
We recommend performing Ethernet frame delay measurements on a stable system.
• The use of Ethernet frame delay measurements on aggregated Ethernet and pseudowire
interfaces is not supported.
• The use of hardware-assisted timestamping is not supported on all MX DPCs (Rev-B
or higher is required).
• If you attempt to perform Ethernet frame delay measurements to a non-MX partner,
the incoming Ethernet frame delay PDUs are discarded silently. Ethernet delay
measurement commands and capabilities are not available on non-MX Series routers.
Related
Documentation
Ethernet OAM •
• Configuring MEP Interfaces to Support ETH-DM on page 128
• Triggering an ETH-DM Session on page 129
• Viewing ETH-DM Statistics on page 130
• Configuring One-Way ETH-DM with Single-Tagged Interfaces on page 131
• Configuring Two-Way ETH-DM with Single-Tagged Interfaces on page 136
• Configuring ETH-DM with Untagged Interfaces on page 140
127 Copyright © 2013, Juniper Networks, Inc.
Chapter 11: ITU-T Y.1731 Ethernet Frame Delay Measurements