Cfd Functions - HP 5130 EI Series Configuration Manual

The local device must send CCM messages carrying the Remote Defect Indication (RDI) flag bits;
otherwise, the peer device cannot sense certain failures. When at least one local MEP in an MA has not
learned all remote MEPs in the MEP list, the MEPs in the MA do not carry the RDI flag bits in CCMs.

CFD functions

CFD functions, which are implemented through the MPs, include:
Continuity check (CC)
•
Loopback (LB)
•
• Linktrace (LT)
Alarm indication signal (AIS)
•
Loss measurement (LM)
•
Delay measurement (DM)
•
Test (TST)
•
Continuity check
Connectivity faults are usually caused by device faults or configuration errors. Continuity check checks
the connectivity between MEPs. This function is implemented through periodic sending of CCMs by the
MEPs. A CCM sent by one MEP is intended to be received by all the other MEPs in the same MA. If a MEP
fails to receive the CCMs within 3.5 times the sending interval, the link is considered as faulty and a log
is generated. When multiple MEPs send CCMs at the same time, the multipoint-to-multipoint link check
is achieved. CCM frames are multicast frames.
Loopback
Similar to ping at the IP layer, loopback verifies the connectivity between a source device and a target
device. To implement this function, the source MEP sends loopback messages (LBMs) to the target MEP.
Depending on whether the source MEP can receive a loopback reply message (LBR) from the target MEP,
the link state between the two can be verified. LBM frames and LBR frames are unicast frames.
LBM frames are multicast and unicast frames. HP devices support sending and receiving unicast LBM
frames and receiving multicast LBM frames. HP devices do not support sending multicast LBM frames. LBR
frames are unicast frames.
Linktrace
Linktrace is similar to traceroute. It identifies the path between the source MEP and the target MP. The
source MEP sends the linktrace messages (LTMs) to the target MP. After receiving the messages, the target
MP and the MIPs that the LTM frames pass send back linktrace reply messages (LTRs) to the source MEP.
Based on the reply messages, the source MEP can identify the path to the target MP. LTM frames are
multicast frames and LTRs are unicast frames.
AIS
The AIS function suppresses the number of error alarms reported by MEPs. If a local MEP does not receive
any CCM frames from its peer MEP within 3.5 times the CCM transmission interval, it immediately starts
sending AIS frames. The AIS frames are sent periodically in the opposite direction of CCM frames. When
the peer MEP receives the AIS frames, it suppresses the error alarms locally, and continues to send the
AIS frames. If the local MEP receives CCM frames within 3.5 times the CCM transmission interval, it stops
sending AIS frames and restores the error alarm function. AIS frames are multicast frames.
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