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, Packet Director 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 Card (PIC)—Physically connects the router to network media such as OC-12/STM-4, OC-48/STM-16, Ethernet, and channelized interfaces. PICs are housed in Flexible PIC Concentrators (FPCs). (Quad-wide PICs, such as the OC-192/STM-64 SONET/SDH PIC, are exceptions. Such PICs occupy an entire FPC slot in the chassis and insert directly into the slot rather than into an FPC card carrier.)
• Flexible PIC Concentrator (FPC)—Processes incoming and outgoing packets. Up to eight FPCs plug into the midplane from the front of the chassis. Each FPC accommodates up to four PICs.
• Packet Forwarding Engine Clock Generator (PCG)—Sends clock signals to the other Packet Forwarding Engine components. Two PCGs plug into the midplane from the rear of the chassis.
• Switching and Forwarding Module (SFM)—Performs route lookup, filtering, and switching. Up to four SFMs plug into the midplane from the rear of the chassis.

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

• Midplane
• Physical Interface Cards (PICs)
• Flexible PIC Concentrators (FPCs)
• Packet Forwarding Engine Clock Generators (PCGs)
• Switching and Forwarding Module (SFM)