3Com S7906E Configuration Manual page 2224

Figure 1-1 Two nested MDs
CFD exchanges messages and performs operations on a per-domain basis. By planning MDs properly
in a network, you can use CFD to locate failure points rapidly.
Maintenance association
A maintenance association (MA) is a set of maintenance points (MPs) in an MD. An MA is identified by
the "MD name + MA name".
An MA serves a VLAN. Packets sent by the MPs in an MA carry the corresponding VLAN tag. An MP
can receive packets sent by other MPs in the same MA.
Maintenance point
An MP is configured on a port and belongs to an MA. MPs fall into two types: maintenance association
end points (MEPs) and maintenance association intermediate points (MIPs).
MEP
Each MEP is identified by an integer called a MEP ID. The MEPs of an MD define the range and
boundary of the MD. The MA and MD that a MEP belongs to define the VLAN attribute and level of the
packets sent by the MEP. MEPs fall into inward-facing MEPs and outward-facing MEPs.
The level of a MEP determines the levels of packets that the MEP can process. The packets transmitted
from a MEP carry the level of the MEP. A MEP forwards packets at a higher level and processes packet
of its level or lower. The processing procedure is specific to packets in the same VLAN. Packets of
different VLANs are independent.
The direction of a MEP determines the position of the MD relative to the port. In
outward-facing MEPs are configured on the two ports. In
configured on the two ports.
An outward-facing MEP communicates through the wire side connected to the port; an inward-facing
MEP communicates through the relay function side.
Figure
1-2
Figure
1-3, inward-facing MEPs are
1-2,