Quality of Service (QoS): Managing Bandwidth More Effectively

Introduction

Introduction

QoS Feature

Default

Menu

CLI

Web

TCP/UDP Priority

Disabled

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page 6-21

Refer to the Online Help.

IP-Device Priority

Disabled

—

page 6-28

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Type-of-Service IP

Disabled

—

page 6-34

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Precedence Mode

 

 

 

 

VLAN-ID Priority

Disabled

—

page 6-46

“

Source-Port Priority

Disabled

—

page 6-52

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DSCP Policy Table

Various

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page 6-58

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As the term suggests, network policy refers to the network-wide controls you can implement to:

■Ensure uniform and efficient traffic handling throughout your network, while keeping the most important traffic moving at an acceptable speed, regardless of current bandwidth usage.

■Exercise control over the priority settings of inbound traffic arriving in and travelling through your network.

Adding bandwidth is often a good idea, but it is not always feasible and does not completely eliminate the potential for network congestion. There will always be points in the network where multiple traffic streams merge or where network links will change speed and capacity. The impact and number of these congestion points will increase over time as more applications and devices are added to the network.

When (not if) network congestion occurs, it is important to move traffic on the basis of relative importance. However, without Quality of Service (QoS) prioritization, less important traffic can consume network bandwidth and slow down or halt the delivery of more important traffic. That is, without QoS, most traffic received by the switch is forwarded with the same priority it had upon entering the switch. In many cases, such traffic is “normal” priority and competes for bandwidth with all other normal-priority traffic, regardless of its relative importance to your organization’s mission. This section gives an overview of QoS operation and benefits, and describes how to configure QoS in the console interface.

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