Data Flow Through the M40 Router Packet Forwarding Engine

Data flows through the M40 router Packet Forwarding Engine in the sequence shown in Figure 17.

Figure 17: M40 Router Packet Forwarding Engine Components and Data Flow

1. Packets arrive at an incoming PIC interface.
2. The PIC passes the packets to the FPC, where the I/O Manager ASIC processes the packet headers, divides the packets into 64-byte data cells, and passes the cells to the backplane.
3. The Distributed Buffer Manager ASIC on the backplane distributes the data cells throughout the memory buffers located on and shared by all the FPCs.
4. The Internet Processor or Internet Processor II ASIC on the SCB performs route lookups and makes forwarding decisions.
5. The Internet Processor or Internet Processor II ASIC notifies a second Distributed Buffer Manager ASIC on the backplane of the routing decision.
6. The Distributed Buffer Manager ASIC forwards the notification to the FPC that hosts the outbound PIC.
7. The I/O Manager ASIC on the FPC reassembles data cells in shared memory into data packets as they are ready for transmission and passes them to the outbound PIC.
8. The outbound PIC transmits the data packets.