Juniper Networks M5 - Manual (Page 28)

Packet Forwarding Engine
Description Value
Weight, minimum configuration 57 lb (25.8 kg)
Thermal output 2550 BTU/hour
Packet Forwarding Engine
The Packet Forwarding Engine is a multicomponent system that uses application-specific
integrated circuits (ASICs) to perform Layer 2 and Layer 3 packet switching, route lookups,
and packet forwarding. The ASICs include the Distributed Buffer Manager ASIC, Internet
Processor II ASIC, I/O Manager ASIC, and media-specific controller ASICs.
The Packet Forwarding Engine has the following components:
•
Midplane—Physically separates front and rear cavities inside the chassis, distributes
power from the power supplies, and transfers packets and signals between router
components, which plug into it.
•
Physical Interface Cards (PICs)—Physically connect the router to network media such
as OC-12/STM-4, OC-48/STM-16, Ethernet, and channelized interfaces.
•
Flexible PIC Concentrators (FPCs)—House PICs. On the M5 and M10 routers, FPCs are
built in (cannot be removed from the chassis as on some other M-series platforms).
•
Forwarding Engine Board (FEB)—Performs route lookup, filtering, and switching. It
installs into the midplane from the rear of the chassis.
For information about Packet Forwarding Engine components, see the following sections:
•
Midplane on page 8
•
Physical Interface Cards (PICs) on page 9
•
Flexible PIC Concentrators (FPCs) on page 10
•
Forwarding Engine Board (FEB) on page 10
Midplane
The midplane is a panel located in the center of the chassis, running from side to side and
forming the rear of the PIC card cage (see Figure 4). All router components 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—After being processed by a PIC, an incoming data packet crosses
the midplane to the FEB. The FEB performs switching and forwarding functions and
transfers outgoing packets back across the midplane to the PICs for transmission
to the network.
8 M5 and M10 Internet Routers Hardware Guide