H3C Technologies H3C S12500 Series Switches - Manual (Page 30)

19
Configuring CFD
Overview
Connectivity Fault Detection (CFD), which conforms to IEEE 802.1ag Connectivity Fault Management
(CFM) and ITU-T Y.1731, is an end-to-end per-VLAN link layer Operations, Administration and
Maintenance (OAM) mechanism used for link connectivity detection, fault verification, and fault location.
Basic concepts in CFD
Maintenance domain
A maintenance domain (MD) defines the network or part of the network where CFD plays its role. An MD
is identified by its MD name.
To accurately locate faults, CFD introduces eight levels (from 0 to 7) to MDs. The bigger the number, the
higher the level and the larger the area covered. Domains can touch or nest (if the outer domain has a
higher level than the nested one) but cannot intersect or overlap.
MD levels facilitate fault location and make fault location more accurate. As shown in
Figure 3 , MD_A
in light blue nests MD_B in dark blue. If a connectivity fault is detected at the boundary of MD_A, any
of the devices in MD_A, including Device A through Device E, might fail. If a connectivity fault is also
detected at the boundary of MD_B, the failure points might be any of Device B through Device D. If the
devices in MD_B can operate correctly, at least Device C is operational.
Figure 3 Two nested MDs
CFD exchanges messages and performs operations on a per-domain basis. By planning MDs correctly
in a network, you can use CFD to rapidly locate failure points.
Maintenance association
A maintenance association (MA) is a part of an MD. You can configure multiple MAs in an MD as
needed. An MA is identified by the "MD name + MA name".