COMNET III CACI
COMNET III CACI
COMNET III CACI
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In the second dimension, the OAM cells are classified by function. The distinction here<br />
is made between performance management, fault management or activation / deactivation<br />
OAM cells. To provide this distinction the fields labeled ‘OAM type’ and ‘Function<br />
type’ in the OAM payload are used. The former field takes the bit-value ‘0001’ for fault<br />
management, the bit-value ‘0010’ for performance management and the bit-value ‘1000’<br />
for activation / deactivation. Each of these classes is further subdivided into several<br />
modes, for which the latter field is used. Performance monitoring operates in the tree<br />
modes: forward monitoring, backward reporting and monitoring and reporting, indicating<br />
in which direction the PM OAM flows 6 . The ‘Function Type’ is set to the bit-values<br />
‘0000’, ‘0001’ and ‘0010’ respectively. For fault management four different modes are<br />
defined: alarm indication signal, remote defect indicator, cell loopback and continuity<br />
check. These four modes as well as their values in the field ‘Function type’ will be<br />
explained in detail below. Finally, the activation / deactivation OAM cell is used to turn<br />
the management functions on and off. ‘Function Type’ here takes the value ‘0000’ to<br />
toggle the activation mode of performance management, and the value ‘0001’ to toggle<br />
the activation mode of fault management. This mode provides an important flexibility to<br />
ATM network management, as will be shown in the next section. Figure 45 summarizes<br />
the functional dimension of the different OAM cell formats.<br />
Header<br />
OAM<br />
Type<br />
Function<br />
Type<br />
Function<br />
Specific<br />
Fields<br />
C<br />
R<br />
C<br />
Fault Management 0001 AIS 0000<br />
RDI 0001<br />
Cell loopback 1000<br />
Continuity Check 0100<br />
Performance Management 0010 Forward monitoring 0000<br />
Backward reporting 0001<br />
Monitoring & reporting 0010<br />
Activation / deactivation 1000 Performance monitoring 0000<br />
Continuity check 0001<br />
Figure 45: OAM Cell Formats in the functionality dimension<br />
6 forward: from VPC/VCC starting point to VPC/VCC end point, backward: from VPC/VCC end point to VPC/VCC<br />
starting point, monitoring and reporting: both directions.<br />
105
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