Juniper M Series User Manual

Figure30: M320 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 Layer 2/Layer 3 Packet Processing
ASIC performs Layer 2 and Layer 3 parsing and divides the packets into 64-byte cells.
3. The Switch Interface ASIC extracts the route lookup key, places it in a notification and
passes the notification to the Internet Processor ASIC. The Switch Interface ASIC also
passes the data cells to the Queuing and Memory Interface ASICs for buffering.
4. The Queuing and Memory Interface ASICs pass the data cells to memory for buffering.
5. The Internet Processor ASIC performs the route lookup and forwards the notification
to the Queuing and Memory Interface ASIC.
6. The Queuing and Memory Interface ASIC sends the notification to the Switch Interface
ASIC facing the switch fabric, unless the destination is on the same Packet Forwarding
Engine. In this case, the notification is sent back to the Switch Interface ASIC facing
the outgoing ports, and the packets are sent to the outgoing port without passing
through the switch fabric (see Step 13).
7. The Switch Interface ASIC sends bandwidth requests through the switch fabric to the
destination port. The Switch Interface ASIC also issues read requests to the Queuing
and Memory Interface ASIC to begin reading data cells out of memory.
8. The destination Switch Interface ASIC sends bandwidth grants through the switch
fabric to the originating Switch Interface ASIC.
Copyright © 2012, Juniper Networks, Inc.130
M Series and T Series Routers Monitoring and Troubleshooting Guide

Juniper M Series Specifications

General

Brand	Juniper
Model	M Series
Category	Network Router
Language	English