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RCA THOMSON SpeedTouchTM (Wireless) Business DSL Router 2.1 What is Quality of Service?

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Chapter 2

Introduction

E-NIT-CTC-20041213-0013v0.5

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2.1 What is Quality of Service?

Definition Quality of Service is the ability for an application to obtain the network service it

requires for successful operation.

Nowadays the total amount of data traffic increases, while new types of data

emerge, like: voice data, video data, audio data. These new types of data pose new

requirements for data transport, e.g. low latency, low data loss… To meet these

requirements, the entire network must ensure them via a connection service

guarantee. Such a connection service guarantee can both be applied to connection-

oriented networks (connection based) and to packet-oriented networks (data-stream

or data type based).

Quality of Service allows specifying a connection service guarantee via a set of

connection parameters. Throughout the network, this set of connection parameters

will be used to handle the connection data in a way to achieve the connection

service guarantee. This handling includes reserving bandwidth, priority based

queuing, scheduling, modifying data characteristics, …

Examples of connection parameters include the maximum amount of bandwidth that

may be used, the guaranteed amount of bandwidth that will always be available, the

maximum delay the data can experience throughout the network, a priority

indication,…

Misunderstandings A common misunderstanding about QoS is that QoS is about gaining a superior level

of network service for particular individuals.

The example below illustrates this.

The best illustration of why it is pointless to give enhanced network service to

particular individuals is shown by video-conferencing. Imagine John: he sees a

horrible quality image of the other video conference participant; but the other

participant sees John’s face perfectly. This is obviously not the desired result.

For John to also see a high-quality image, all participants in the video conference

need appropriate network service, not only John.

IP QoS provides such service. With IP QoS voice and/or video traffic can get a higher

priority then data traffic. This way good voice and video quality is guaranteed.

!Note that QoS is no solution for overloaded networks, it only helps to shape

bursty peaks on the network. (See Bandwidth versus QoS )

Contents

Main Page Page Page Contents Contents 4 6 Meters, queues and IPQoS......................................... 59 7 Scenario 1: Residential user.......................................85 Page Page About this IPQoS Configuration Guide About this IPQoS Configuration Guide ! Page Chapter 1 1 Document scope Page 2Introduction 2.1 What is Quality of Service? Definition Misunderstandings ! Page 2.2 Relative versus Guaranteed QoS Types of QoS 3 Basic QoS Concepts 3.1 Precedence and TOS Introduction First generation Precedence values Second generation 3.2 Differentiated Services Differentiated Services domain 3.3 Classification and conditioning principles Introduction classifier Traffic classification Traffic conditioning Page 3.4 Differentiated Services Code Point (DSCP) Introduction Per Hop Behaviour Standardized PHBs Page Assured Forwarding (AF) PHB Group: 4 IP QoS Framework Overview 4.1 Main Framework Components Graphical overview QoS Components 4.2 Resource Management Mapping to internal class 5 Packet Classification and Labelling 5.1 Classification Introduction Terminology 5.1.1 Order of classification rules Introduction Routing classification Sub-chains ! Page 5.2 Labels Introduction CLI Command groups ! Label command group Adding a label Label parameters Debug command group 5.2.1 Label parameters explained Introduction Classification Defclass Page Page 5.2.2 Using TOS, DSCP or Precedence Introduction Precedence TOSmarking TOS DSCP 5.2.3 Forwarding parameters. Introduction TTLoverwrite TTL Modify the label parameters Page 5.3 Rules 5.3.1 Rules parameters explained Introduction Srcintf Chain Index Srcip Dstip Serv Page The flush command 5.3.2 Rule debug commands Introduction Traceconfig Traceconfig result Stats 5.4 Chains Page 5.4.1 Define a relation between chains 5.5 Expressions Page Bridgeport Addr Precedence Tos Dscp ! Srcportend Dstport Icmptype Dstportend Page Page 6 Meters, queues and IPQoS 6.1 Meters and queues 6.2 The IPQoS command group Overview IPQoS command group EF command group meter command group Page Page Page MTU explained. EF stats command EF list command Line Speed 6.4 Meter command group Introduction Adding a meter 6.4.1 Meter config command Meter parameters meter config Label Meter config parameters explained Name Intf Droprate Markrate Burst Page Dscp Precedence Class Classification Meter delete command Meter list command Meter start command Meter stop command Meter flush command Meter stats command 6.4.2 Packet flow Illustration Classification Metering 6.5 Queue command group Introduction Queue config command 6.5.1 Queue config parameters explained Dest Ecnmarking Queue Propagate Data ACK1Data DataACK2 Example Maxpackets Respackets Maxbytes Resbytes Hold Markprob Queue list command Queue stats command Queue clear command 6.6 IPQoS Command group Introduction ipqos config command 6.6.1 Ipqos config parameters explained Introduction Dest Discard State ! Priority Realtimerate Burstsize Weight Maxpackets Maxbytes Ipqos list command 7 Scenario 1: Residential user. 7.1 Configuring labels and rules for VoIP. Introduction The web interface Labels Rules Expressions Page 7.2 Configuring labels and rules for DSCP. Introduction Labels Rules Expressions 7.3 Configuring labels and rules for Interactive traffic. Introduction Labels Page Expressions Page Page 8 Scenario 2: Business user with TOS marking. ! 8.1 Labels Page Page Page 8.2 Rules. Page Page Page Page Page Page Page Page 8.3 IPQoS per PVC Page Page Chapter 9 9 Scenario 3: Metering Page Reference List Reference List Page Abreviation List Abreviation List