Packet Forwarding Engine
M40 Internet Router Hardware Guide
10
Backplane
The backplane is a panel that forms the back of the FPC card cage (see Figure 3). The SCB
and all the FPCs install into the backplane from the front of the chassis. The backplane
contains a temperature sensor and is cooled by three fans operating in unison. It also
contains an EEPROM that stores the serial number and revision level of the backplane.
The backplane performs the following functions:
Power distribution—The backplane distributes power to all router components from the
power supplies attached to it.
Signal connectivity—The backplane transports the signals exchanged by system
components for monitoring and control purposes.
Management of shared memory on the FPCs—One Distributed Buffer Manager ASIC on
the backplane uniformly allocates incoming data packets throughout shared memory on
the FPCs.
Transfer of outgoing data cells to the FPCs—A second Distributed Buffer Manager ASIC
on the backplane passes data cells to the FPCs for reassembly into packets when the
data is ready to be transmitted.
Figure 3: The Backplane
Physical Interface Cards (PICs)
Physical Interface Cards (PICs) are housed on Flexible PIC Concentrators (FPCs) and
physically connect the router to network media. For information about FPCs, see “Flexible
PIC Concentrators (FPCs)” on page 11. The router supports various PICs, including ATM,
Channelized OC-12/STM-4, Gigabit Ethernet, and SONET/SDH interfaces. Up to four PICs
install in each FPC. The PIC slots are numbered
0
(zero) through
3
, top to bottom.
PICs receive incoming packets from the network and transmit outgoing packets to the
network, performing framing and line-speed signaling for their media type as required. PICs
also encapsulate outgoing packets received from the FPCs before transmitting them. The
controller ASIC on each PIC performs additional control functions specific to the PIC media
type.
Backplane
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