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.
• Flexible PIC Concentrators (FPCs)—Process incoming and outgoing packets. Up to four FPCs plug into the midplane from the front of the chassis. Each FPC accommodates up to four PICs.
• Physical Interface Cards (PICs)—Physically connect the router to network media such as OC12/STM4, OC48/STM16, Ethernet, and channelized interfaces. PICs are housed in Flexible PIC Concentrators (FPCs). (Quad-wide PICs, such as the 4-port Gigabit Ethernet and OC48/STM16 SONET/SDH PICs, are an exception. Such PICs occupy an entire FPC slot in the chassis and insert directly into the slot rather than into an FPC card carrier.)
• System and Switch Board (SSB)—Performs route lookup, filtering, and switching. One or two SSBs plug into the midplane from the front of the chassis.

For information about Packet Forwarding Engine components, see the following sections:

• Midplane
• Physical Interface Cards (PICs)
• Flexible PIC Concentrators (FPCs)
• System and Switch Board (SSB)