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Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
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Chapter 7 Circuits and Tunnels
Virtual Concatenated Circuits
Note Although LCAS operations are errorless, an SDH error can affect one or more VCAT members. If this
occurs, the VCAT Group Degraded (VCG-DEG) alarm is raised. For information about clearing this
alarm, refer to the “Alarm Troubleshooting” chapter in the Cisco ONS 15310-MA SDH Troubleshooting
Guide.
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 is necessary when interoperating with the ONS 15454
ML-Series cards. SW-LCAS uses legacy SDH failure indicators like path alarm indication signal
(AIS-P) and path remote defect indication (RDI-P) to detect member failure. You can select SW-LCAS
during VCAT circuit creation.
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 service states, all In Group non-LCAS
members must have cross-connects in the same service state. A non-LCAS circuit can mix Out of Group
and In Group members if the In Group members are in the same service state. Non-LCAS members do
not support the locked-enabled,outOfGroup service state; to put a non-LCAS member in the Out of
Group VCAT state, use locked-enabled,disabled.
Note Protection switching for LCAS and non-LCAS VCAT circuits might exceed 60 ms. Traffic loss for VC
low-order path VCAT circuits is approximately two times more than traffic loss for a VC high-order path
VCAT circuit. You can minimize traffic loss by reducing path differential delay.
7.7.4 VCAT Circuit Size
Table 7-6 lists supported VCAT circuit rates and the number of members for each card.
Use the Members tab in the Edit Circuit window to add or delete members from a VCAT circuit. The
capability to add or delete members depends on whether the VCAT circuit is LCAS, SW-LCAS, or
non-LCAS:
• For VCAT LCAS circuits, you can add or delete members without affecting service. Before deleting
a member, Cisco recommends that you put the member in the locked-enabled,outOfGroup service
state.
Table 7-6 ONS 15310-MA SDH Card VCAT Circuit Rates and Members
Card Circuit Rate Number of Members
CE-100T-8 1
1. A VCAT circuit with an ONS 15310-MA SDH CE-100T-8 or ML-100T-8 card as a source
or destination and an ONS 15454 ML-Series card as a source or destination can have only
two members.
VC12 1–63
VC3 1-3
ML-100T-8 1VC3 1–2
CE-MR-6 VC12 1-63
VC3 1-21
VC4 1-7