Cisco XR 12410 - Manual (Page 24)

Chapter 1 Product Overview
Switch Fabric and Alarm Card Overview
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Cisco XR 12410 and Cisco XR 12810 Router Installation Guide
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Switch Fabric Card Functionality
Routers ship from the factory with 2 CSCs and 5 SFCs installed in the 7 slots in
the switch fabric and alarm card cage (see
Figure 1-2 ).
• CSCs are installed in slot 0 (CSC0) or slot 1 (CSC1).
• SFCs are installed in slot 2 (SFC0), slot 3 (SFC1), slot 4 (SFC2),
slot 5 (SFC3), and slot 6 (SFC4).
Note The enhanced version of the CSC and SFC cards is required for support of BITS,
Single Router APS and Dual Priority features. The enhanced version of the cards
cannot be mixed with the original version fabric cards.
Clock Scheduler Card
Clock scheduler cards provide the following functionality:
• Scheduler—Handles all scheduling requests from the line cards for access to
the switch fabric.
• System clock—Supplies the synchronizing signal to all SFCs, line cards, and
the RP. The system clock synchronizes data transfers between line cards or
between line cards and the RP through the switch fabric.
• Switch fabric—Carries user traffic between line cards or between the RP and
a line card. The switch fabric on the CSC is identical to the switch fabric on
the SFC.
The second CSC provides redundancy for the data path, scheduler, and reference
clock. Traffic between the line cards and the switch fabric is monitored constantly.
If the system detects a loss of synchronization (LOS), it automatically activates
the data paths on the redundant CSC so data flows across the redundant paths. The
switch to the redundant CSC occurs within sub-seconds (the actual switch time
depends on your configuration and its scale).