LYU9802Quality of Service in Wired/Wireless Communication Networks: Techniques and Evaluation

Supervisor: Dr. Michael R. Lyu

Marker: Dr. W.K. Kan

Wan Yung Chun and Lam Shu Yin

Overview

Objectives Introduction to Quality of Service (QoS)QoS ParametersPerformance Evaluation

About Generic QoS Ethernet and wireless LAN environment Interconnected network with RSVP router

Future Works

Objectives

Provides a complete QoS solution in network Network level (ATM, RSVP router) System level (GQoS, our QoS scheme) Application level (COBRA, building QoS application)

From this project, we can learn: How to evaluate the performance of a system How to design a good scheme System programming experiences Distributed programming in COBRA

QoS Definitions

The collective effect of service performances which determine the degree of satisfaction of a user .

The guarantee a network makes to an application in terms of providing a certain contracted level of service through out the application session.

Represents quantities,e.g. transfer rate, how long does the receiver have to wait for complete transmission, error rate, lost rate.

Importance of QoS Growth of real-time

network application is fast.

Growth of bandwidth cannot catch up the needs.

Simply expanding bandwidth is not effective.

Solution: Good management of bandwidth.

Problem of old management of bandwidth

TCP guarantees reliability and sequence TCP uses reactive congestion control IP offers only a best-effort model of serviceNo guarantees can be made to Real-Time and

Multimedia Traffic

Current support of QoSApplication Level - IP Navigator

Commercial product, enhancing current IP protocol provides QoS network management.

System Level - Windows 98 Provides Generic QoS

Network Protocol Level - IPv6 Flow label (20 bits) and priority field (8 bits), instead of

4 class of TOS settings (8 bits).

Medium Access Sublayer Level - ATM ATM supports QoS data transfer

Use of QoS

Mobile communicationReal-time video and sound transmissionInteractive applications on networkRouting for traffic with performance guaran

teesQoS-aware ATM application

QoS Parameters

What is its function? An adequate measure for the service quality provided b

y a network

QoS Mapping Perceptual QoS Application QoS Network QoS

QoS Mapping

Network QoS Specification

QoS Specifications

Metrics Policies

Security Performance Relative Management Levels of

Importance Services

Timeliness Precision Accuracy Combinations

LatencyJitterBurst Tolerance

Amount of datatransmitted

ReliabilityConnectionfailure probability

ThroughputPeak bandwidth

Best effortGuaranteedControlled load

ConfidentialityIntegrity

Performance Evaluation of Generic Quality of Service in Microsoft Windows 98®

What is GQOS? Microsoft's implementation of Quality of Service (QO

S)

Levels of Service (LoS) Best effort Guaranteed Controlled load

Why we choose GQoS?

Powered by Microsoft, it will soon be accepted as an industrial standard for QoS

GQoS is flexible and can run on any network environment, including wireless network

It lies on ReSerVation Protocol, which many network products begin to support it

Evaluation of GQoS

Methodology of the experiment:

•Program QOSEVENT•Source Sample program from Microsoft with our

enhancement•Version May 1998•Environment Ethernet and Wireless network

Types of experiments:

•One sender and one receiver•Two senders and one receiver

One sender and one receiverComparison of different levels of service in Ethernet environment using GQoS

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Best effortGuaranteedControlled load

QoS disabled transmission takes the longest time.

Guaranteed transmission

remains stable all over

the transmission.

Best effort always takes the shortest time to complete.

Two senders and one receiverTime period(in millisecond)

Level of service 1 2 3 4 5 6 7 8 9 10 Avg

QoS disabled 8290 7960 5870 6210 6150 6210 7690 8130 8300 7200 7201Best effort - - 5440 - 5330 5600 5550 5330 5280 5270 5400

Variation of transmission time between QoS enabled and disabled successive transfer

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QoS disabledBest effort

QoS disabled transmission always have a greater variation in trans

mission time.

OthersThree senders and one receiver experiment was

done and similar result was obtained.Other finding,

Importance of factors affecting the transmission time:

This is due to the slow start feature of TCP congestion control.

Whether the transmission is the current activated job in Windows.

First to occupy the channel > Activation factor > Use of QoS

Wireless LAN

Network Configuration:Notebook computer

Wireless LAN

Proxim access point (base station)

Ethernet

Desktop computer

Experiment Measures

The Ethernet is connected to the access point and the desktop computer only

Fix the position of the notebook and the access point

Use program to start the measuring routineRepeat the experiment several times

One sender and one receiverComparison of different levels of service in wireless environment using GQoS

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QoS disabled

Best effort

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Controlled load

Two senders and one receiver

Transmission time between QoS enabled and disabled successive transfer

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As the packet size issmall, the OS scheduleralso pay a role in theperformance

Findings in Wireless LAN

Two different best effort data streams running simultaneously will compete one another

Two different guarantee data streams match the user specification

Wired LANs with router

Network Configuration:

Sender’s Computer

RSVP-aware Router

Receiver’s Computer

Best effort VS Guaranteed

Transmission Time of best effort and guaranteed service running at thesame time with packet size 128K

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Findings in GQoS Evaluation

The behaviour of GQoS in wireless environment is similar to that in wired environment except the bandwidth are different.

In Ethernet and wireless LAN environment, only the packet scheduler inside GQoS pay a role in providing services

When networks are interconnected by RSVP routers, the routers help GQoS to classify packets and hence give a better guaranteed service

Future WorksEvaluation part

Point out the weakness of GQoS Building QoS applications in Windows

Implementation in System Level Purpose a new QoS scheme on Linux Implement our own QoS scheme which lies on RSVP a

nd compare it with GQoS

Implementation in Application Level Provide QoS in COBRA and build a QoS manager at C

OBRA service level

Q & A Session

Please feel free to ask

The End

Thank you