nada: a unified congestion control scheme for real-time media
DESCRIPTION
NADA: A Unified Congestion Control Scheme for Real-Time Media. Xiaoqing Zhu and Rong Pan Advanced Architecture & Research Cisco Systems August 2012. Agenda. Design goals System model Network node operations Sender / Receiver behavior Evaluation results Open issues. Packet loss. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/1.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 1Cisco Confidential 1© 2011 Cisco and/or its affiliates. All rights reserved.
NADA: A Unified Congestion Control Scheme
for Real-Time Media
Xiaoqing Zhu and Rong Pan
Advanced Architecture & Research
Cisco Systems
August 2012
![Page 2: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/2.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2
Agenda
• Design goals
• System model
• Network node operations
• Sender/Receiver behavior
• Evaluation results
• Open issues
![Page 3: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/3.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3
Design Goal #1:Limit Self-Inflicted Delay
network queue network queue
Time
Congest
ion
win
dow
Siz
e
Packet loss
Time
Rate
React early
![Page 4: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/4.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4
Design Goal #2:Leverage A Suite of Feedback
Mechanisms
Delay-based ECN-based
PCN-based
none existing feature
new feature
Network Support
Perf
orm
an
ce
Existing loss-basedschemes
![Page 5: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/5.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5
Design Goal #3:Weighted Bandwidth Sharing
Relative bandwidth
Application-level priority
Bandwidth sharing among flows:
![Page 6: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/6.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6
video playout
optimal rate calculation
encoderrate control
RTCP report
video packets
network node
measure delay/marking
sender receiver
target rate
update networkcongestion notification
System Overview
rate shaping buffer
bufferlevel
![Page 7: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/7.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7
Network Node Behavior
• Queuing discipline: FIFO
• Congestion notification via:
Delay: no special operation at the queue
ECN: queue-based random marking
PCN: token-bucket-based random marking
![Page 8: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/8.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8
Queue-based ECN Marking
if :
no marking
else if :
else:
mark all packets
update: Avg. Queue OccupancyM
ark
ing P
robabili
ty
![Page 9: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/9.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9
Token-bucket-based PCN Marking
upon packet arrival:
meter packet against token bucket ;
update token level
if :
no marking
else if :
else:mark all packets
Remaining Token BucketM
ark
ing P
robabili
ty
![Page 10: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/10.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10
target rate
Sender Structure
target rate calculation
encoderrate control
video packets
rate shaping buffer
sending rate calculation
RTCP report(loss/delay/ECN/PCN)
bufferlevel
videorate
![Page 11: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/11.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11
Target Rate Calculation
• Reacting to delay: session priority
queuing delay
marking ratio
• Reacting to ECN/PCN marking:
scaling parameter
scaling parameter
![Page 12: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/12.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12
Sending Rate Calculation
• Accommodate lag in encoder reaction
• Trade-off between between network queuing and rate shaping delay
scaling parameter
encoder reaction time
![Page 13: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/13.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13
Slow-Start Rate
start time
time horizon
Time
Rate
![Page 14: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/14.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14
Receiver Behavior
• Observe instantaneous end-to-end per packet statistics:
Queuing delay:
ECN/PCN marking:
• Obtain time-smoothed estimations:
• Periodic RTCP reports (e.g., at 3% of received packets)
![Page 15: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/15.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15
Test Scenario
• Bottleneck bandwidth: 30Mbps
• Random delay measurement error for stream 6, at time t=30s
Flow ID
1 1 2 1
2 1 2 1
3 2 6 1
4 2 6 2
5 3 5 2
6 3 5 2
7 2 4 3
8 2 4 3
9 3 6 3
10 3 6 3
![Page 16: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/16.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16
Delay-Based Adaptation: Per-flow Rate
Stream 6 delay measurement error
Weighted BW sharing
![Page 17: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/17.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17
Delay-Based Adaptation: Total Rate
Fast convergence
![Page 18: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/18.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18
Delay-Based Adaptation: Bottleneck Queue
Low standing queue
![Page 19: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/19.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19
Delay-Based Adaptation: Packet Loss Ratio
No persistent losses
![Page 20: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/20.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20
Delay vs. ECN: Per-Flow RateECN-BasedDelay-Based
![Page 21: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/21.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21
Delay ECN
Delay vs. ECN: Bottleneck Queue
![Page 22: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/22.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22
ECN vs. PCN: Per-Flow RateECN PCN
Smoother streaming rates
![Page 23: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/23.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23
ECN vs. PCN: Total RateECN PCN
Slight under-utilization
No losses
![Page 24: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/24.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24
ECN PCN
ECN vs. PCN: Bottleneck Queue
Zero standing queue
![Page 25: NADA: A Unified Congestion Control Scheme for Real-Time Media](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56813c90550346895da63b1c/html5/thumbnails/25.jpg)
© 2010 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 25
Conclusions and Next Steps
• Key benefits of NADA: Fast rate adaptationWeighted bandwidth sharingCan work with a range of congestion signalsIn case of PCN: zero standing queue and smoother streaming rates
• Next steps: Future evaluations in linux-based implementationsGraceful transition between different congestion signalsCompete robustly against loss-based schemes