Midplane

The midplane is a panel located in the center of the chassis, running from side to side and forming the rear of the FPC card cage (see Figure 4). All router components other than PICs plug directly into the midplane. The midplane contains an EEPROM that stores the serial number and revision level of the midplane.

The midplane performs the following functions:

• Transfer of packets—The midplane accepts an incoming packet after it is processed by an FPC, and transmits it to an SFM. The SFM performs switching and forwarding functions and transfers outgoing packets back across the midplane to the FPCs for transmission to the network.
• Power distribution—The midplane distributes power to all router components from the power supplies attached to it.
• Signal connectivity—The midplane transports the signals exchanged by system components for monitoring and control purposes.