Setting Up Loopback Messages
  • 24 Jan 2024
  • 3 Minutes to read
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Setting Up Loopback Messages

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Article Summary

Loopback messages are unicast frames transmitted by a MEP. Sending a high volume of loopback messages can test the bandwidth, reliability or jitter of a service. A MEP can send a loopback to any MEP or MIP in the service. Loopback messages are discussed in IEEE 802.1ag.

To start the loopback messages

  1. Access the page SOAM ▶CFM ▶MEP ▶LBM.
    All existing loopback messages for Maintenance association End Points are displayed.

  2. Click the MEPID of the MEP for which you want to start the LBM.

  3. Complete the required fields, then click Start.

For more information on specific parameters, refer to the following table.

MEP Loopback (SOAM ▶CFM ▶MEP ▶LBM)

ParameterDescription
MEP Index

Index

Index assigned to the Maintenance association End Point.
MEPIDMaintenance association End Point Identifier.
ActiveIndicates whether a loopback request is active for that MEP.
Target TypeLoopback target by remote MEPID or MAC address.
Remote MEPIDTarget remote MEPID. The remote MEP MAC address is resolved into the local MEP database.
MAC AddressTarget MAC address. Only Unicast MAC address are valid for link trace target address.
VLAN PriorityIndicates how to determine the LBM VLAN priority value:
  • CCM Priority: Use the same priority that MEP CCMs.
  • Specific: Use a specific value specified by the Priority field.
PriorityThe value assigned to the LBM VLAN priority.

Range: 0–7

VLAN Drop EligibilityValue for LBM VLAN drop eligibility bit. Checking this box sets the DEI bit to 1.
Nbr MessageNumber of LBMs to send.
IntervalThe interval, expressed in milliseconds, between LBMs.

Range: 100–5000

Data TLVIndicates whether LBMs should include a Data Type Length Value (TLV). Possible values are:
  • None: No Data TLV included
  • Incremental: A Data TLV with incremental byte values is included
  • Pattern: A Data TLV based on a user data pattern is included.
LengthAmount of data, expressed in bytes, inside the data TLV.

Range: 1–1488 bytes

PatternUser data pattern for the Data TLV.

Format: ASCII characters

Bottom of Table

ParameterDescription
Loopback RequestIndicates whether a loopback request is active or inactive for that MEP.
Target MAC AddressThe target MAC address used for the latest loopback request.
Latest Start TimeThe time the latest loopback request was initiated for that MEP.
Latest End TimeThe time the latest loopback request has completed or was stopped for that MEP.
Next Seq. #The sequence number for the next LBM initiated from that MEP.
Nbr LBM Requested

LBM Requested

The number of LBM requested for the latest loopback request.
Nbr LBM SentThe number of LBM sent for the latest loopback request. When the loopback is not active, this number should be the same as the number of LBM requested. If not, this implies the loopback request was stopped by a management command.
Nbr LBR Received

LBM Received

The number of loopback replies (LBR) received for the latest loopback request.
LBR with Bad MSDUThe number of LBR received with a content that did not match the corresponding LBM for the latest loopback request.
Nbr LBR DuplicatedThe number of LBR received with a sequence number already received for the latest loopback request.
Packet loss ratioThe computed packet loss ratio for the latest loopback request.
Nbr Packets LostThe number of missing LBR for the latest loopback request.
Nbr GapsThe number of times a sequence of LBRs went missing during the latest loopback request.
Largest Gap SizeThe longest uninterrupted sequence of missing packets that was detected during the most recent loopback request.
Nbr LBR Out of OrderThe number of times an LBR was received during the latest loopback request whose sequence number did not match the expected value.

Viewing Loopback Message Information

To view the loopback message information

  1. Access the page SOAM ▶CFM ▶MEP ▶LBM.

  2. Click the MEPID of the MEP for which you want to view LBM information.

For more information on specific parameters, refer to the "MEP Loopback (SOAM ▶CFM ▶MEP ▶LBM)" table.

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