Juniper EX9200 Series User Manual

CHAPTER 3
Packet Flow Through the CoS Process
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Packet Flow Through the CoS Process Overview on page 15
Packet Flow Through the CoS Process Overview
Perhaps the best way to understand Junos CoS is to examine how a packet is treated on
its way through the CoS process. This topic includes a description of each step and figures
illustrating the process.
The following steps describe the CoS process:
1. A logical interface has one or more classifiers of different types applied to it (at the
[edit class-of-service interfaces] hierarchy level). The types of classifiers are based
on which part of the incoming packet the classifier examines (for example, EXP bits,
IEEE 802.1p bits, or DSCP bits). You can use a translation table to rewrite the values
of these bits on ingress.
NOTE: You can only rewrite the values of these bits on ingress on the
Juniper Networks M40e, M120, M320 Multiservice Edge Routers, and T
Series Core Routers with IQE PICs. For more information about rewriting
the values of these bits on ingress, see Configuring ToS Translation Tables.
2. The classifier assigns the packet to a forwarding class and a loss priority (at the [edit
class-of-service classifiers] hierarchy level).
3. Each forwarding class is assigned to a queue (at the [edit class-of-service
forwarding-classes] hierarchy level).
4. Input (and output) policers meter traffic and might change the forwarding class and
loss priority if a traffic flow exceeds its service level.
5. The physical or logical interface has a scheduler map applied to it (at the [edit
class-of-service interfaces] hierarchy level).
At the [edit class-of-service interfaces] hierarchy level, the scheduler-map and
rewrite-rules statements affect the outgoing packets, and the classifiers statement
affects the incoming packets.
15Copyright © 2013, Juniper Networks, Inc.

Juniper EX9200 Series Specifications

General

Product Series	EX9200 Series
Model	EX9204, EX9208, EX9214
Port Density	48 ports per line card
Jumbo Frame Size	9216 bytes
Power Supply	AC or DC
Redundant Power Supplies	Yes
Redundant Fans	Yes
Operating System	Junos OS
Form Factor	Chassis
Maximum Virtual LANs	4096
Redundancy	Yes
Redundancy Options	Power and fan redundancy
Management	CLI, SNMP
Operating Temperature	32° to 104° F
Storage Temperature	-40°F to 158°F (-40°C to 70°C)
Humidity	5 to 95% non-condensing
MTBF	Over 100, 000 hours
Switch Type	Modular Chassis Switch
Latency	Less than 5 µs

Summary

About the Documentation

Documentation and Release Notes

Obtain the latest technical documentation and release notes from Juniper Networks.

Supported Platforms

Lists hardware platforms supported by the document's features.

Using the Examples in This Manual

Guide to using configuration examples with 'load merge' commands.

Merging a Full Example

Step-by-step instructions for merging a complete configuration example.

Merging a Snippet

Step-by-step instructions for merging a partial configuration snippet.

Documentation Conventions

Explains icons, text, and syntax conventions used in the guide.

Documentation Feedback

How to provide feedback to improve the documentation.

Requesting Technical Support

Information on contacting JTAC for technical product support.

Self-Help Online Tools and Resources

Details Juniper's online portal for problem resolution and support.

Opening a Case with JTAC

How to open a support case with JTAC via web or telephone.

PART 1 Overview

CoS Overview

Introduces Class of Service (CoS) and its importance in network traffic management.

CoS Input and Output Configuration

Explains how CoS components map inputs to outputs for traffic configuration.

Packet Flow Through the CoS Process

Describes packet treatment through Junos OS Class of Service.

CHAPTER 1 CoS Overview

CoS Standards

Outlines industry standards (RFCs) for Junos OS Class of Service capabilities.

Understanding Packet Flow Across a Network

Explains how CoS classifies traffic and affects packet flow.

Junos CoS Components

Details the various components of Junos OS Class of Service features.

Default CoS Settings

Describes default Class of Service settings applied by Junos OS.

CoS Applications Overview

Discusses how CoS features can be configured for various application needs.

Interface Types That Do Not Support CoS

Lists interface types with limited or no CoS support.

VPLS and Default CoS Classification

Explains default CoS classification for VPLS routing instances.

CHAPTER 2 CoS Input and Output Configuration

CoS Inputs and Outputs Overview

Explains how CoS components map inputs to outputs for traffic configuration.

CHAPTER 3 Packet Flow Through the CoS Process

Packet Flow Through the CoS Process Overview

Details packet treatment through the Junos OS Class of Service process.

PART 2 Configuration

Configuration Statements

Introduces configuration statements for Junos OS network setup.

CHAPTER 4 Configuration Statements

[edit chassis] Hierarchy Level

Details Junos OS configuration statements for the chassis hierarchy.

[edit class-of-service] Hierarchy Level

Details Junos OS configuration statements for the class-of-service hierarchy.

[edit firewall] Hierarchy Level

Details Junos OS configuration statements for the firewall hierarchy.

[edit interfaces] Hierarchy Level

Details Junos OS configuration statements for the interfaces hierarchy.