Figure 9-2 Mds At Different Levels - Raisecom ISCOM2600G-HI (A) Series Configuration Manual

Raisecom
ISCOM2600G-HI (A) Series Configuration Guide
CFM concepts
CFM consists of following components:

Maintenance Domain (MD), also called Maintenance Entity Group (MEG), is a network that
runs CFM. It defines network range of OAM management. MD has a level property, with 8
levels (level 0 to level 7). The bigger the number is, the higher the level is and the larger the
MD range is. Protocol packets in a lower-level MD will be discarded after entering a higher-
level MD. If no Maintenance association End Point (MEP) but a Maintenance association
Intermediate Point (MIP) is in a high-level MD, the protocol can traverse the higher-level MD.
However, packets in a higher-level MD can traverse lower-level MDs. In the same VLAN
range, different MDs can be adjacent, embedded, but not crossed.
As shown in Figure 9-2, MD 2 is in MD 1. Packets in MD 1 need to traverse MD 2. Configure
MD 1 to be at level 6, and MD 2 to be at level 3. Then packets in MD 1 can traverse MD 2
and implement connectivity fault management of the whole MD 1. However, packets in MD 2
cannot diffuse into MD 1. MD 2 is a server layer while MD 1 is a client layer.

Figure 9-2 MDs at different levels


The service instance is also called Maintenance Association (MA). It is a part of a MD. One
MD can be divided into one or multiple service instances. One service instance corresponds to
one service and is mapped to a group of VLANs. VLANs of different service instances cannot
cross. Though a service instance can be mapped to multiple VLANs, one service instance can
only use a VLAN for sending or receiving OAM packets. This VLAN is the master VLAN of
the service instance.

As shown in Figure 9-3, the MEP is an edge node of a service instance. MEPs can be used to
send and process CFM packets. The service instance and the MD where the MEP locates
decide VLANs and levels of packets received and sent by the MEP.
For any device that runs CFM on the network, the MEP is called local MEP. For MEPs on
other devices of the same service instance, they are called Remote Maintenance association
End Points (RMEP).
Multiple MEPs can be configured in a service instance. Packets sent by MEPs in one instance
carry an identical S-VLAN Tag, priority, and C-VLAN Tag. A MEP can receive OAM packets
sent by other MEPs in the instance, intercept packets at the same or lower level, and forward
packets of a higher level.
MD
Service instance
MEP
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