H3C Technologies H3C S10500 Series Switches - Manual (Page 28)

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By cooperating with MEPs, a MIP can perform a function similar to ping and traceroute. Like a MEP, a
MIP forwards packets of a different level without any processing and only processes packets of its level.
Figure
6 demonstrates a grading example of the CFD module. Six devices, labeled A through F
respectively, exist. Suppose each device has two ports, and MEPs and MIPs are configured on some of
these ports. Four levels of MDs are designed in this example, the bigger the number, the higher the level
and the larger the area covered. In this example, Port 1 of device B is configured with the following
MPs—a level 5 MIP, a level 3 inward-facing MEP, a level 2 inward-facing MEP, and a level 0
outward-facing MEP.
Figure 6 Levels of MPs
Device A Device B Device C Device D Device E Device F
5 5
3
5 5
3 3 3
2 2 2 2
0 0 0 0 0 0
MD level 5
MD level 3
MD Level 2 MD Level 2
MD level 0
Port
5 Outward-facing MEP and MD level
5 MIP and MD level
Maintenance association
Logical path of CFD messages
Port 1 Port 2
MD level 0 MD level 0
3 Inward-facing MEP and MD level
2 2 2 2
MEP list
A MEP list is a collection of local MEPs allowed to be configured and the remote MEPs to be monitored
in the same MA. It lists all the MEPs configured on different devices in the same MA. The MEPs all have
unique MEP IDs. When a MEP receives from a remote device a continuity check message (CCM) that
carries a MEP ID not included in the MEP list of the MA, it drops the message.
CFD functions
CFD works effectively only in properly-configured networks. Its functions, which are implemented through
the MPs, include:
• Continuity check (CC)
• Loopback (LB)
• Linktrace (LT)
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 continuity
check messages (CCMs) by the MEPs. As a multicast message, 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