Cisco ONS 15454 SDH Manual page 27

Chapter 11 Circuits and Tunnels
Figure 11-11 VCAT Common Fiber Routing
VCAT
Function
ML-Series
VCAT
Function
CE-Series cards also support split fiber routing, which allows the individual members to be routed on
different fibers or each member to have different routing constraints. This mode offers the greatest
bandwidth efficiency and also the possibility of differential delay, which is handled by the buffers on the
terminating cards. Four protection options are available for split fiber routing: Fully Protected, PCA,
Unprotected, and DRI.
Figure 11-12 VCAT Split Fiber Routing
VCAT
Traffic
Function
Source VCAT at NE
11.16.3 Link Capacity Adjustment
The CE-100T-8 supports the link capacity adjustment scheme (LCAS), which is a signaling protocol that
allows dynamic bandwidth adjustment of VCAT circuits. When a member fails, a brief traffic hit occurs.
LCAS temporarily removes the failed member from the VCAT circuit for the duration of the failure,
leaving the remaining members to carry the traffic. When the failure clears, the member circuit is
automatically added back into the VCAT circuit without affecting traffic. You can select LCAS during
VCAT circuit creation.
Instead of LCAS, the FC_MR-4 (enhanced mode), CE-1000-4, CE-MR-10, and ML-Series cards support
Software–Link Capacity Adjustment Scheme (SW-LCAS), which uses legacy SONET failure indicators
like the AIS-P and RDI-P to detect member failure. If used, SW-LCAS removes the failed member from
the VCAT circuit for the duration of the failure, leaving the remaining members to carry the traffic. When
the failure clears, the member circuit is added back into the VCAT circuit. SW-LCAS cannot
78-18119-01
Member 1
VC-1
VCG-1
VC-2
Member 2
Member 1
VC-3
VCG-2
VC-4
Member 2
Figure 11-12
Virtually
Concatenated
Group
VC-1
VC-2
Intermediate
NE
VC-3
VC-4
shows an example of split fiber routing.
Intermediate
Member #1
NE
Member #2
Intermediate
NE
Intermediate
Member #3
NE
Cisco ONS 15454 SDH Reference Manual, R8.5
11.16.3 Link Capacity Adjustment
Member 1
VCAT
VCG-1
Function
Member 2
Member 1
VCAT
VCG-2
Function
Member 2
VCAT
Function
with
Differential
Delay Buffer
Destination VCAT at NE
ML-Series
Traffic
11-27