Guidelines for Configuring Routers to Support an ETH-DM Session
Keep the following guidelines in mind when configuring routers to support an Ethernet frame delay measurement (ETH-DM) session:
Configuration Requirements for ETH-DM
You can obtain ETH-DM information for a link that meets the following requirements:
- The measurements can be performed between peer maintenance association endpoints (MEPs) on two routers.
- The two MEPs must be configured on two Ethernet physical interfaces or on two Ethernet logical interfaces. For more information, see Configuring a Maintenance Endpoint and Configuring a Remote Maintenance End Point.
- The two MEPs must be configured—on their respective routers—under the same maintenance association (MA) identifier. For more information, see Creating a Maintenance Association.
- On both routers, the MA must be associated with the same maintenance domain (MD) name. For more information, see Creating the Maintenance Domain.
- On both routers, periodic packet management (PPM) must be running on the Routing Engine and Packet Forwarding Engine, which is the default configuration. You can disable PPM on the Packet Forwarding Engine only. However, the Ethernet frame delay measurement feature requires that distributed PPM remain enabled on the Packet Forwarding Engine of both routers. For more information about ppm, see the JUNOS Routing Protocols Configuration Guide.
- If the PPM process (ppm) is disabled on the Packet Forwarding Engine, you must re-enable it. Re-enabling distributed ppm entails restarting the ethernet-connectivity-fault-management process, which causes all connectivity fault management (CFM) sessions to re-establish. For more information about CFM sessions, see Configuring Ethernet Local Management Interface.
 | Note: The Ethernet frame delay measurement feature is supported only for MEPs configured on Ethernet physical or logical interfaces on DPCs in MX Series routers. The ETH-DM feature is not supported on aggregated Ethernet interfaces or LSI pseudowires. |
Configuration Options for ETH-DM
By default, the ETH-DM feature calculates frame delays using software-based timestamping of the ETH-DM PDU frames sent and received by the MEPs in the session. As an option that can increase the accuracy of ETH-DM calculations when the DPC is loaded with heavy traffic in the receive direction, you can enable hardware-assisted timestamping of session frames in the receive direction.
| Note: Hardware-assisted timestamping for ETH-DM frames is only supported for MEP interfaces on Enhanced DPCs and Enhanced Queuing DPCs in MX Series routers. |
