Product Overview 1-45
Overview of the Cisco 12008
As a multi-function board, the CSC provides the following system services:
•Provides one plane of switch fabric for the router (see the section below entitled “Switch
Fabric in the Cisco 12008”).
•Serves as a switch fabric controller card for the router (see the section below entitled
“Switch Fabric Controller Functions of the CSC”).
•Serves as an alarm monitoring facility for the router (see the section below entitled
“Housekeeping and Alarm Monitoring Functions of the CSC”).
•Provides onboard power for its own electronic circuitry, as well as power and control
functions for the fan trays (see the section below entitled “Board Power and Fan Tray
Power Functions of the CSC”).
These functions are described in the following sections.

Switch Fabric in the Cisco 12008

A switch plane in the router consists of one OC-12-rate crossbar in the backplane that
enables each line card slot in the router to be connected logically to every other line card
slot. Line cards installed in any combination of slots in the upper card cage can
communicate with each other by means of the router’s switch fabric.
The switch fabric of the router constitutes the totality of the possible data paths that can be
established through the router. The magnitude of the router’s switch fabric (and, hence, its
data- carrying capacity) is related directly to the number of switch planes that are made
available to the router for data-handling purposes. By installing a second CSC and/or the
optional set of three SFCs in the router, you can increase the number of switch planes
present in the router, thereby increasing the magnitude of the router’s over all switc h fa bric.
Table1-7 outlines the possible configurations of CSCs and SFCs and the router switching
capacity that results from these configurations.