D-Link xStack Reference Manual page 116

xStack® DES-3200 Series Layer 2 Ethernet Managed Switch WEB UI Reference Guide
An Outward facing MEP source frames toward the bridge port and can only be configured on routed ports. An
Outward facing port drops all CFM frames at it level or lower coming from the bridge relay function side. It processes
all CFM frames at its level, and drops all CFM frames at a lower level, coming from the bridge port. An Outward facing
port forwards all CFM frames at higher levels regardless of which direction the frames come in. If the port on which the
outward MEP is configured is blocked by Spanning-Tree Protocol, the MEP can still transmit and receive CFM
messages through the bridge port.
A MIP is a maintenance point that is internal to an MD, not at the boundary. A MIP receives CFM frames from other
MIPs and from MEPs. These frames are cataloged and forwarded using the bridge relay function and bridge port. All
CFM frames at a lower level than the MIP are blocked and dropped regardless of the origin. All CFM frames at a
higher level are forwarded regardless of the origin. If the port on which a MIP is configured is blocked by Spanning-
Tree Protocol, the MIP cannot receive CFM messages or relay them toward the bridge relay function side. The MIP
can, however, receive and respond to CFM messages from the bridge port.
CFM messages include Continuity Check Messages (CCMs), Loopback Messages (LBMs) and Link Trace Messages
(LTMs). CFM uses standard Ethernet frames that can be sourced, terminated, processed and relayed by bridges.
Routers support limited CFM functions.
Continuity Check Messages (CCMs) are multicast messages exchanged among MEPs. CCMs allow discovery of
MEPs for other MEPs within a domain and allow MIPs to discover MEPs. CCMs are confined to a maintenance
domain. CCMs are cataloged by MIPs are the same maintenance level and terminated by remote MEPs at the same
maintenance level. They are unidirectional (no response solicitation) and carry the status of the port on which the MEP
is configured. LBMs are similar to Ping or ICMP messages in that they indicate only whether a destination is reachable
and do not allow discovery of each hop.
Link Trace Messages (LTMs) are multicast CFM frames sent by MEPs to identify adjacency relationships with
remote MEPs and MIPs at the same maintenance level. The message body of an LTM includes a destination MAC
address of a target MEP that terminates the linktrace. When a MIP or MEP receives an LTM, it generates a unicast
Link Trace Reply (LTR) to the initiating MEP. It also forwards the LTM to the target MEP destination MAC address. An
LTM effectively traces the path to the target MEP or MIP.
Loopback Messages (LBMs) are similar to Ping or ICMP messages in that they indicate only whether a destination is
reachable and do not allow the discovery of each hop.
.

Maintenance Association (MA) – Boundaries of an Administrator's scope of monitoring part of the network

Maintenance Domain (MD) – A level of monitoring within the hierarchy

Maintenance End Points (MEP) – End Points of the MA or MD

Maintenance Intermediate Points (MIP) – Intermediate Points within MA or MD
Note: CE = Customer Equipment
Figure 3 - 59. OAM Domain Architecture
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