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Traffic Sensitive Active Queue Management

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Internet was not designed to support application based quality of service (QoS) ... Thus, advantage of labeling packets with high delay hints is neutralized ... – PowerPoint PPT presentation

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Title: Traffic Sensitive Active Queue Management


1
Traffic Sensitive Active Queue Management
  • - Mark Claypool, Robert Kinicki, Abhishek Kumar
  • Dept. of Computer Science
  • Worcester Polytechnic Institute
  • Presenter Ashish Samant

2
Introduction
  • 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.

3
Introduction
  • Spectrum of QoS Requirements of Applications

Streaming Video
Interactive Video
Throughput Sensitivity
File Transfer
Streaming Audio
Web-browsing
Interactive Audio
Gaming
Electronic Mail
Delay Sensitivity
4
Introduction
  • 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.

5
Outline
  • Introduction
  • TSQ Mechanism
  • Application Quality Metrics
  • Experiments and Results
  • Future Work

6
TSQ Mechanism
3
2
1
4
7
TSQ Mechanism
AQM
10 Mbps
q

(hint)

q
TSQ
q
p


5 Mbps
p
Packet queue
10 Mbps
8
TSQ Mechanism
  • On receiving each packet, router calculates a
    weight
  • w (d td ) / 2N ta
  • d delay limit
  • td drain time
  • N no. of bits used to represent delay hints
  • ta arrival time
  • Weight of packet determines its position in
    router queue.
  • Lower delay hint leads to lower weight.
  • Time of arrival prevents starvation.

9
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.

10
TSQ 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 delay
  • q instantaneous queue position
  • q new queue position
  • p drop probability calculated by underlying AQM
  • Packets that cut-in-line more will have a
    higher drop probability.

11
Outline
  • Introduction
  • TSQ Mechanism
  • Application Quality Metrics
  • Experiments and Results
  • Conclusion and Future Work

12
Application Quality Metrics
  • Based on previous work, we measure application
    quality as minimum of its 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.

13
Application Quality Metrics
Interactive Audio Delay Quality Refs
Act02IKK93
Excellent Quality
Good Quality
Excellent Quality
Bad Quality
Good Quality
Bad Quality
14
Application Quality Metrics
Interactive Audio Throughput Quality RefsCor98
15
Outline
  • Introduction
  • TSQ Mechanism
  • Application Quality Metrics
  • Experiments and Results
  • Conclusion and Future Work

16
Experimental Setup
Network Topology
S1
D1
50 Mbps, 50 ms
S2
50 Mbps, 50 ms
D2
R1
R2
B Mbps
SN-1
DN-1
DN
SN
17
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.

18
Experiment 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.

19
Analysis 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.

20
Analysis Interactive Audio
  • Throughput measured every RTT (300 ms).
  • Median throughput low for lower delay hints.

21
Analysis Interactive Audio
Overall Quality
  • Overall quality is minimum of delay and
    throughput quality.
  • Maximum quality occurs when delay hint is 6.

22
Conclusions
  • 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.

23
Future 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.

24
  • Questions or Comments ?
  • Thank you !
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