10 Understanding QoS

8/7/2019 10 Understanding QoS

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1999, Cisco Systems, Inc.www.cisco.com

Module 10:Understanding

Quality of Service

Module 10:Understanding

Quality of Service


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10-2CSE: Networking FundamentalsQoS 1999, Cisco Systems, Inc.www.cisco.com

Agenda

What Is QoS?

QoS Building Blocks

QoS in Action


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The ability of the network to

provide better or special service

to users/applications.

Consistent PredictablePerformance

Data, Video, Voice

What Is Quality of Service (QoS)?What Is Quality of Service (QoS)?


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What Is Quality of Service (QoS)?

DesktopConferencing,DistanceLearning

Mission-CriticalApplications

E-Mail

FileTransfer

Classification

Policing

Shaping

Congestionavoidance


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10-5CSE: Networking FundamentalsQoS 1999, Cisco Systems, Inc.www.cisco.comSource: Forrester, August 1998, Fortune 1000

What Is Driving the Needfor QoS?

What Is Driving the Needfor QoS?

0 20 40 60 80 100

ission-Critical Apps

oice

ideo

None

Other


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Enterprise ResourcePlanning (ERP) applications

rder entry

Finance

Manufacturing

Human resources

Supply-chain management

Sales-force automation

What else is mission critical?

SNA applications

Selected physical ports

Selected hosts/clients

What Are Mission-CriticalApplications?

What Are Mission-CriticalApplications?


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QoS BenefitsQoS Benefits

Control network resources

Improve cost efficiency

Increase WAN efficiency Minimize administrative overhead

Create a business-enabling

technology foundation Combine mission-critical,

voice, and video applications


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Where Is QoS Important?

No

1 %

YesYes8 %8 %

WAN

No%YesYes

5 %5 %

LAN

Source: Forrester, August 1998, Fortune 1000


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LAN QoS RequirementsAre Emerging

QoS is beneficial when there is linkcongestion and for buffer management

Points of substantial speed mismatch and

points of aggregation are congestioncandidates

Prerequisite to multimedia deployment isthe need to prioritize mission-criticalapplications

Buffering reduces loss but delay-sensitiveapplication could be negatively impacted

Such as Ethernet transmit queue:1 K at 10 Mbps --> 1 8-ms delay


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TrainingServers

VideoVideo

Network ResourcesNetwork ResourcesWhoWho

ERPERP 3 5 x x 73 5 x x 7

MMF, 9F, 955< 100 KB< 100 KB

HighHigh

WhenWhenQuality of ServiceQuality of Service

VoIPVoIP MMF, 9F, 955< 150 ms< 150 ms

ProductManager

CampusBackbonePublicFrame Relay

rder Entry,Finance,

Manufacturing

SalesManager

RemoteCampus

QoS ExampleQoS Example


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1999, Cisco Systems, Inc.www.cisco.comwww.cisco.com 1999, Cisco Systems, Inc.

QoS Building BlocksQoS Building Blocks


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Session 1Session Session 3 Session

SQLnet

FTP

SNA

HTTP

Weighted Fair Queuing

Automatically allocates bandwidth fairly

Congestion ManagementFancy Queuing

Congestion ManagementFancy Queuing

ther queuing options include FIF ,

priority queuing, and custom queuing


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TransmitBufferQueue

Random Early Detection (RED)Random Early Detection (RED)

RED reduces long-term average queue

Packet dropsare randomizedthroughoutqueue depth

Drop rate isincreased as queuedepth is increased


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Packets classifiedPackets classifiedas gold are droppedas gold are droppedat 90% queue depth.at 90% queue depth.

Packets classifiedPackets classifiedas blue start droppingas blue start droppingat a 50% queue depth.at a 50% queue depth.

Drop rate is increased asDrop rate is increased asqueue depth is increased.queue depth is increased.

Queue

Weighted REDWeighted RED

WRED addresses:

In the event packets

need to be dropped,what class ofpackets shouldbe dropped


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InterfaceBuffers

Discard Based n:

Buffer Queue Depth

QoS Assignment

FIF Scheduling

Pass

Fail

TransmitQueue

utputLine

DiscardDiscardTestTest

Weighted RandomEarly Detection (WRED)

Weighted RandomEarly Detection (WRED)


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QoS Signalling:Resource Reservation Protocol

Reserve

1-Mbps BWon this line

I need 1-MbpsBW and

00-ms delay

This app needs

1-Mbps BW and

00-ms delay

Reserve1-Mbps BW

on this

network


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No quality of service Resources consumed

by other applications

Unmanaged traffic

Example: No Quality of ServiceExample: No Quality of Service

ClientVideoServer

Jittery


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Reserves bandwidth end-to-end

Guarantees delay-sensitive applications

Must be supported on clients, servers,and routers

Example: With Quality of ServiceRSVP

Example: With Quality of ServiceRSVP

ClientVideo

Server

This app. needs1-Mbps BW and

00-ms delay

Reserve1-Mbps BWon this line




I need 1-MbpsBW and

00- ms delayClear!


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End-to-End QoS

80 .1p:

Traffic Filtering

for Switching

Campus NetworkRemote Site

Mainframe

Smart

Queuing

Policy Routing

RSVP For

End-End Reservation

Traffic Shaping

Leased Line

Traffic Shaping

Link Fragmentation

and Interleaving

Intranet

FR or ATM

Services


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Where to Apply QoS FeaturesWhere to Apply QoS Features

QoS

Core

Access

Switch

Aggregation

Router

Backbone

Router

C-3Fast

EthernetFast

Ethernet

QoS IngressQoS Ingress

Classification Classification

QoS WAN EdgeQoS WAN Edge

Admission

Control

Classification Congestion

Avoidance

Congestion

Management

Admission

Control

Classification Congestion

Avoidance

Congestion

Management

QoS CoreQoS Core

Congestion

Avoidance

CongestionManagement

Congestion

Avoidance

CongestionManagement


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1999, Cisco Systems, Inc.www.cisco.comwww.cisco.com 1999, Cisco Systems, Inc.

QoS in ActionQoS in Action


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SiSi

Set Telephony = High T S= 5

Set Game = Low

T S =

For T S = 5For T S = 5

Threshold =

High Priority Queue

(70% Transmit Ratio,

Low Delay)

For T S =For T S =

Threshold =

Low Priority Queue

(30% Transmit Ratio,High Delay)

SiSi

Example 1: Prioritizationof IP Telephony

Example 1: Prioritizationof IP Telephony


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SQL Listener

Database 10.1. .

Database 10.1. .1

Server FarmServer FarmSwitchSwitch

BackboneBackboneSwitchSwitch

AccessAccessSwitchSwitch

UntrustedUntrustedClientClient

ReclassifyTCP, L -Port = 15 1Set T S = 5Drop Threshold=Low

Q S IngressQ S Ingress Q S CoreQ S Core

ScheduleAccordingto T S = 5

ClientClientQ S IngressQ S IngressQ S CoreQ S Core

Server Farm

Reclassify IF:L -Port = 15 1

IP-SA/DA = 10.1. .1

IP-SA/DA = 10.1. .

Set T S = 5

Schedule

According to

T S = 5

SQL Client

Example : ERP ApplicationExample : ERP Application


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Summary

QoS provides guaranteed availability

Prioritization of mission-critical versusnoncritical applications

Interactive and time-sensitive applications Voice, video, and data integration

Key QoS building blocks

classification

policing

shaping

congestion avoidance


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26Presentation_ID 1999, Cisco Systems, Inc. www.cisco.com

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10 Understanding QoS