lyu9802 quality of service in wired/wireless communication networks: techniques and evaluation...
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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
0
500
1000
1500
2000
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3500
4000
4500
5000
1 2 3 4 5 6 7 8
Tim
e us
ed to
sen
d a
pack
et (i
n m
illis
ec)
QoS disabled
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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200
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1 2 3 4 5 6
Var
iatio
n (in
mill
isec
)
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
0
2
4
6
8
10
12
1 2 3 4 5 6 7 8 9 10
Tim
e us
ed to
sen
d a
pack
et (i
n se
cond
)
QoS disabled
Best effort
Guaranteed
Controlled load
Two senders and one receiver
Transmission time between QoS enabled and disabled successive transfer
0
50
100
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200
250
1 2 3 4 5 6 7 8 9
Tra
nsm
issi
on T
ime
(in
mil
lise
c)
QoS disabled
Best effort
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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3500
1 4 7 10 13 16 19 22 25 28
i-th packet
Sing
le trip
tim
e
Best Effort
Guaranteed
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