Cisco SR2016T-NA Reference Manual page 762

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Performance Routing Engine Overview

Forwarding Path

The forwarding path (FP) assembly is a unique blend of hardware and microcoded processors that

provides high forwarding rates with considerable flexibility for future growth in packet processing

features. The FP is centered around a pair of PXF network processors, which are custom Cisco-designed

multiprocessor ASICs. Each PXF processor provides a packet processing pipeline that contains

16 microcoded processors, arranged as multiple pipelines.

Each of the 16 processors in a PXF network processor is an eXpress Micro Controller (XMC), which is

an independent, high-performance processor that is customized for packet processing. Each XMC

processor provides a sophisticated dual-instruction-issue execution unit that is programmed to perform

a specific packet-processing task in the most efficient manner. The exact processing function assigned

to each XMC is flexible and can change as new features are added to the Cisco IOS software.

Within each PXF network processor, the 16 XMC processors are linked together in four parallel

pipelines, which each pipeline contains four XMC processors arranged as a systolic array. Each XMC

processor performs its own particular function and then passes its results to its neighboring downstream

The two PXF network processors are linked to form four parallel packet-processing pipelines, each

containing eight XMC processors in a row. See

The PXF network processor architecture in the PRE module allows all 32 XMC processors to process

multiple packets independently and efficiently, yielding high throughput while still allowing substantial

feature processing. The PRE module architecture centralizes the main packet processing, freeing up the

other line cards to perform localized processing.

Cisco Broadband Cable Command Reference Guide

Performance Routing Engine Block Diagram

Performance routing engine

Route processor

64 to 512 MB

interface and

Forwarding Path PXF Processor Arrays

Forwarding path

PXF network processor

forwarding path

Backplane interface and

buffer management

Links to line cards

Commands for the Cisco uBR10012 Router

Broadband cable