Fortwo-way (round-trip) Ethernet frame delaymeasurement, either MEP can send a
requestto begin a two-way delay measurementto its peer MEP, which responds with
timestampinformation. Run-time statistics are collectedand displayed at the initiator
MEP.The clocks do not needto be synchronized at the transmitting and receiving MEPs.
TheJunos OS supports the optional timestamps in delay measurement reply(DMR)
framesto increase the accuracyof delay calculations. The Junos OS also supports
hardware-assistedtimestamping for Ethernet framedelay protocol data units (PDUs)
inthe reception path.
Usethe show commands at the initiator MEP to displaytwo-way delay statistics, and at
thereceiver MEP to display one-way delaystatistics.
Thefollowing are some limitations with regardto using Ethernet frame delay
measurement:
Thisfeature is availableonly on MX Series routers.
Ethernetframe delay measurements are availableonly when the distributed periodic
packetmanagement daemon (ppmd) is enabled.
Thestatistics collected arelost after graceful Routing Engine switchover(GRES).
Youcan monitor only one sessionto the same remote MEP or MAC address.
Accuracyis compromised when the systemchanges (such as from reconfiguration).
Werecommend performing Ethernet frame delaymeasurements on a stable system.
Theuse of Ethernetframe delay measurements on aggregatedEthernet and pseudowire
interfacesis not supported.
Theuse of hardware-assisted timestamping is not supportedon all MX DPCs (Rev-B
orhigher is required).
Ifyou attempt to perform Ethernet frame delaymeasurements to a non-MX partner,
theincoming Ethernet frame delay PDUs are discarded silently.Ethernet delay
measurementcommands and capabilities are not availableon non-MX routers.
Related
Documentation
MXSeries Ethernet Services Routers SolutionsPage
ConfiguringMEP Interfaces to Support ETH-DM on page122
Triggeringan ETH-DM Session on page 123
ViewingETH-DM Statistics on page 124
ConfiguringOne-Way ETH-DM with Single-TaggedInterfaces on page125
ConfiguringTwo-WayETH-DM with Single-TaggedInterfaces on page 130
ConfiguringETH-DM with Untagged Interfaces on page134
121Copyright© 2010, Juniper Networks,Inc.
Chapter11: ITU-T Y.1731Ethernet Frame Delay Measurements