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Cisco ONS 15454 Reference Manual, R8.5.x
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Chapter 11 Circuits and Tunnels
11.18.3 Link Capacity Adjustment
Note The switch time values shown in Table 11-16 does not include differential delay. The maximum
differential delay for CE100T-8 is 122ms. This differential delay is added to the switch time to
get the maximum time.
11.18.3 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.
Note Although LCAS operations are errorless, a SONET er ror can affect one or more VCAT members. If this
occurs, the VCAT Group Degraded (VCG-DEG) alarm is raised. For information on clearing this alarm,
refer to the Cisco ONS 15454 Troubleshooting Guide.
Instead of LCAS, the FC_MR-4 (enhanced mode), CE-1000-4 card, and ML-Series cards support
software LCAS (SW-LCAS). SW-LCAS is a limited form of LCAS that allows the VCAT circuit to adapt
to member failures and keep traffic flowing at a reduced bandwidth. SW-LCAS uses legacy SONET
failure indicators like AIS-P and remote defect indication, path (RDI-P) to detect member failure.
SW-LCAS removes the failed member from the VCAT circuit, leaving the remaining members to carry
the traffic. When the failure clears, the member circuit is automatically added back into the VCAT
circuit. For ML-Series cards, SW-LCAS allows circuit pairing over two-fiber BLSRs. With circuit
pairing, a VCAT circuit is set up between two ML-Series cards: one is a protected circuit (line
protection) and the other is a PCA circuit. For four-fiber BLSRs, member protec tion cannot be mixed.
You select SW-LCAS during VCAT circuit creation. The FC_MR-4 (line rate mode) does not support
SW-LCAS.
In addition, you can create non-LCAS VCAT circuits, which do not use LCAS or SW-LCAS. While
LCAS and SW-LCAS member cross-connects can be in different s ervice states, all In Group non-LCA S
members must have cross-connects in the same service state. A non-LCAS circuit can mix Out of Group
and In Group members, as long as the In Group members are in the same service state. Non-LCAS
members do not support the OOS-MA,OOG service state; to p ut a non-LCAS member in the Out
of Group VCAT state, use the OOS-MA,DSBLD administrative state.
Table 11-16 Switch Times
Type of circuit For CE100T-8 in ms
CCAT 60
HO VCAT 90
HO LCAS190
LO VCAT 202
LO LCAS 202
1. The calculated number for HO LCAS includes all the inherent delays of the protocol. Also the CE-100-T numbers are for a
group size of only three members.