Miscellaneous Control Subsystem (MCS)

The Miscellaneous Control Subsystem (MCS) works with its companion Routing Engine to provide control and monitoring functions for router components. It also generates a clock signal for the SONET/SDH interfaces on the router.

One or two host modules (paired MCS and Routing Engine) can be installed into the midplane from the rear of the chassis, as shown in Figure 3. Only one host module is active at a time, with the optional second host module in standby mode. For more information about host module interdependence and redundancy, see Host Module.

The MCS performs the following functions:

• Monitoring and control of router components—The MCS collects statistics from all sensors in the system. When it detects a failure or alarm condition, it sends a signal to the Routing Engine, which generates control messages or sets an alarm. The MCS also relays control messages from the Routing Engine to the router components.
• Controlling component power-up and power-down—The MCS controls the power-up sequence of router components as they start, and powers down components when their offline buttons are pressed.
• Signaling of mastership—In a router with more than one host module, the MCS signals to all router components which host module is the master and which is the standby. It relays the mastership signal for the two PCGs as well.
• Providing SONET/SDH clock source—The MCS generates a 19.44-MHz SONET/SDH clock signal, along with a signal that indicates which MCS is the master SONET/SDH clock generator (if two MCSs are installed).
• Clock monitoring—The MCS monitors the PCG system clock and its SONET/SDH clock to verify that they are providing the expected signal. It generates an alarm if a clock signal is incorrect.
• Control of FPC resets—If the MCS detects errors in an FPC, it attempts to reset the FPC. After three unsuccessful reset attempts, the MCS takes the FPC offline and informs the Routing Engine. Other FPCs are unaffected, and system operation continues.

MCS Components

Each MCS (shown in Figure 10) has the following components:

• PCI interface—Connects the MCS to the Routing Engine.
• 100-Mbps Ethernet switch—Carries signals and monitoring data between router components.
• 19.44-MHz stratum 3 reference clock—Generates clock signal for SONET/SDH PICs.
• I²C controller—Monitors the status of router components.
• Three LEDs—Indicate MCS status. There is a blue one labeled MASTER, a green one labeled OK, and an amber one labeled FAIL. Table 8 describes the LED states.
• Offline button—Prepares the MCS for removal from the router when pressed.
• Extractor clips—Control the locking system that secures the MCS in the chassis.

Table 8: States for MCS LEDs