Setting Up Loopback Messages

Updated on 25 Feb 2022
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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

Access the page SOAM ▶ CFM ▶ MEP ▶ LBM.
All existing loopback messages for Maintenance association End Points are displayed.
Click the MEPID of the MEP for which you want to start the LBM.
Complete the required fields, then click Start.

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

MEP Loopback (SOAM ▶ CFM ▶ MEP ▶ LBM)

Parameter	Description
MEP Index Index	Index assigned to the Maintenance association End Point
MEPID	Maintenance association End Point Identifier
Active	Indicates whether a loopback request is active for that MEP
Target Type	Loopback target by remote MEPID, MAC address or Multicast
Remote MEPID	Target remote MEPID. The remote MEP MAC address is resolved into the local MEP database.
MAC Address	Target MAC address. Only Unicast MAC address are valid for link trace target address.
VLAN Priority	Indicates how to determine the LBM VLAN priority value: <UL CCM Priority: Use the same priority that MEP CCMs. Specific: Use a specific value specified by the Priority field.
Priority	The value assigned to the LBM VLAN priority Range: 0-7
VLAN Drop Eligibility	Value for LBM VLAN drop eligibility bit. Checking this box sets the DEI bit to 1.
Nbr Message	Number of LBMs to send
Interval	The interval, expressed in milliseconds, between LBMs Range: 100–5000
Data TLV	Indicates 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.
Length	Amount of data, expressed in bytes, inside the data TLV Range: 1–1488 bytes
Pattern	User data pattern for the Data TLV Format: ASCII characters

Bottom of Table

Parameter	Description
Loopback Request	Indicates whether a loopback request is active or inactive for that MEP
Target MAC Address	The target MAC address used for the latest loopback request
Latest Start Time	The time the latest loopback request was initiated for that MEP
Latest End Time	The 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 Sent	The 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 MSDU	The number of LBR received with a content that did not match the corresponding LBM for the latest loopback request
Nbr LBR Duplicated	The number of LBR received with a sequence number already received for the latest loopback request
Packet loss ratio	The computed packet loss ratio for the latest loopback request
Nbr Packet Lost	The number of missing LBR for the latest loopback request
Nbr Gaps	The number of times a sequence of LBRs went missing during the latest loopback request
Largest Gap Size	The longest uninterrupted sequence of missing packets that was detected during the most recent loopback request
Nbr LBR Out of Order	The number of times an LBR was received during the latest loopback request whose sequence number did not match the expected value

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