traffic sensitive active queue management
DESCRIPTION
Traffic Sensitive Active Queue Management. - Mark Claypool, Robert Kinicki, Abhishek Kumar Dept. of Computer Science Worcester Polytechnic Institute Presenter – Ashish Samant. Introduction. Internet was not designed to support application based quality of service (QoS). Best effort model - PowerPoint PPT PresentationTRANSCRIPT
Traffic Sensitive Active Queue Management
- Mark Claypool, Robert Kinicki, Abhishek Kumar
Dept. of Computer Science
Worcester Polytechnic Institute
Presenter – Ashish Samant
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IntroductionIntroduction
Internet was not designed to support application based quality of service (QoS).
– Best effort model– No performance guarantees
Active Queue Management (AQM) helps deal with congestion at routers, but is not enough.
– No per application QoS– Not sensitive to delay/throughput needs
Our goal, “to add per application based QoS to AQM, over current best effort Internet”.
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IntroductionIntroduction
Spectrum of QoS Requirements of ApplicationsT
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ghpu
t S
ens
itivi
ty
Delay Sensitivity
Electronic Mail
File TransferWeb-browsing Streaming Audio
Streaming Video
Gaming
Interactive Video
Interactive Audio
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IntroductionIntroduction
Problems with previous approaches to AQM:– Static classification– Per flow state maintenance– Pricing, policing overhead
Features of Traffic Sensitive QoS (TSQ):– Allows applications to indicate delay/throughput sensitivity
at packet level.– Can be deployed over existing AQM schemes.– No significant addition to overhead at routers.
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OutlineOutline
Introduction
TSQ Mechanism
Application Quality Metrics
Experiments and Results
Future Work
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TSQ MechanismTSQ Mechanism
Router
RoutingTable
Packetqueue
1
23
4
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TSQ MechanismTSQ Mechanism
AQM
Packet queue
10 Mbps
10 Mbps
5 Mbps
q
q’=
TSQ
(hint)
q’p +
p’
=
+ q+Rate
+
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TSQ MechanismTSQ Mechanism
On receiving each packet, router calculates a weight :w = (d * td ) / 2N + ta
d = delay limittd = drain time
N = no. of bits used to represent delay hintsta = arrival time
Weight of packet determines it’s position in router queue.
Lower delay hint leads to lower weight. Time of arrival prevents starvation.
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TSQ Mechanism TSQ Mechanism
TSQ uses “cut-in-line” scheme to insert packets with high delay sensitivity (higher weights) towards the front of the queue.
Packets from throughput sensitive application are delegated to the back of the queue
Packets that “cut-in-line” are dropped with a higher probability to ensure fairness.
Thus, advantage of labeling packets with high delay hints is neutralized with higher drop rates.
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TSQ MechanismTSQ Mechanism
The underlying AQM has a drop probability (p) that is applied uniformly to all packets.
Delay sensitive packets receive higher drop probability :
p’ = [(l + q)2 * p ] / (l + q’)2
l = one way delayq = instantaneous queue position
q’ = new queue positionp = drop probability calculated by underlying AQM
Packets that “cut-in-line” more will have a higher drop probability.
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OutlineOutline
Introduction
TSQ Mechanism
Application Quality Metrics
Experiments and Results
Conclusion and Future Work
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Application Quality MetricsApplication Quality Metrics
Based on previous work, we measure application quality as minimum of it’s delay quality (Qd) and throughput quality (Qt) :
Q(d,t) = min(Qd, Qt) { 0 ≤ Q(d,t) }
Higher value of Qd indicates the application is more sensitive to delay and vice versa.
Application quality is normalized between 0 and 1 - 1 indicates highest quality and 0 means no quality
at all.
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Application Quality MetricsApplication Quality Metrics
Excellent Quality Good Quality
Bad Quality
Excellent Quality
Good QualityBad Quality
Interactive Audio Delay Quality Refs [Act02][IKK93]
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Application Quality MetricsApplication Quality Metrics
Interactive Audio Throughput Quality Refs[Cor98]
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OutlineOutline
Introduction
TSQ Mechanism
Application Quality Metrics
Experiments and Results
Conclusion and Future Work
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Experimental SetupExperimental Setup
Network TopologyS1
S2
SN-1
SN
Queue Size
PI, PI+TSQAQM
800 packets
qref200 packets
R1
50 Mbps, 50 ms
D1
D2
DN-1
DN
R2
50 Mbps, 50 ms
B Mbps
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Experimental Setup Experimental Setup
PI parameters : a = 0.00001822, b = 0.00001816, w = 170 Hz, qref = 200 packets, qmax = 800 packets.
Average packet size = 1000 bytes.
All experiments run for 100 seconds
TSQ parameters : l = 40 ms. This is one-way delay constant parameter.
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Experiment – Interactive AudioExperiment – Interactive Audio
Experiment 1: Interactive Audio
– Bottleneck link bandwidth = 15 Mbps– 100 sources and 100 destinations. One
way propagation delay = 150 ms– 99 TCP based file transfer flows using
delay hint = 16– 1 TCP friendly CBR source sending at 128
Kbps, with varying delay hints.
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Analysis – Interactive AudioAnalysis – Interactive Audio
Analysis - Interactive Audio ( Delay )
• Low median queuing delay for lower delay hint.
• Less variation in queuing delay at lower delay hints.
•Delay Quality increases as delay hints decrease.
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Analysis – Interactive AudioAnalysis – Interactive Audio
• Throughput measured every RTT (300 ms).
• Median throughput low for lower delay hints.
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Analysis – Interactive Audio Analysis – Interactive Audio
Overall Quality
• Overall quality is minimum of delay and throughput quality.
• Maximum quality occurs when delay hint is 6.
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ConclusionsConclusions
TSQ provides a per-packet QoS to Internet applications.
It is a best-effort service without any guarantees.
Trade-off between throughput and delay is maintained by adjusting queue position and drop probability.
Does not require complex modifications at the router, over those needed for the AQM.
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Future WorkFuture Work
Derive quality metrics for other applications like network games, instant messaging, peer to peer.
Develop applications to dynamically change their delay hints.
Investigate optimum number of bits to be used for delay hints.
Apply TSQ to other domains, for e.g. wireless.
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Questions or Comments ?
Thank you !