Datasheet

11-26
Cisco ONS 15454 SDH Reference Manual, R7.0
October 2008
Chapter 11 Circuits and Tunnels
11.15.3 Link Capacity Adjustment
Figure 11-11 VCAT Common Fiber Routing
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 shows an example of split fiber routing.
Figure 11-12 VCAT Split Fiber Routing
11.15.3 Link Capacity Adjustment
The CE-100T-8 card 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, 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
Member 1
VCG-2
Member 2
124265
Intermediate
NE
Member 1
VCG-1
Member 2
Member 1
VCG-2
Member 2
Member 1
VCG-1
Member 2
VCAT
Function
VCAT
Function
VCAT
Function
VCAT
Function
VC-1
VC-2
VC-3
VC-4
VC-1
VC-2
VC-3
VC-4
ML-Series ML-Series
124065
VCAT
Function
Source VCAT at NE
Traffic Traffic
Virtually
Concatenated
Group
Member #1
Member #2
Member #3
Intermediate
NE
VCAT
Function
with
Differential
Delay Buffer
Destination VCAT at NE
Intermediate
NE
Intermediate
NE