TCP Video Streaming to Bandwidth-Limited Access Links

1
TCP Video Streaming to Bandwidth-Limited Access
Links

• Puneet Mehra and Avideh Zakhor
• Video and Image Processing Lab
• University of California, Berkeley

2
Talk Outline

• Goals Motivation
• Our Approach
• Experimental Results
• Related Work
• Conclusion

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Goal

• Efficient video streaming using TCP to
  bandwidth-limited receivers
• Key Assumptions
• Receivers have limited-bandwidth last mile
  connections to Internet
• and run multiple concurrent TCP networking apps
• Constraints
• Should not modify senders or network
  infrastructure

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Motivation

• Increasingly access links are the net.
  Bottleneck!
• Limited Bandwidth (B/W) ? Less than 1.5MBps
• Users run concurrent apps ? compete for limited
  B/W
• Most Traffic on Internet is TCP HTTP, P2P, FTP
• TCP handles recovery of lost packets
• TCP has congestion control
• UDP Streaming difficult w/ firewalls
• Problem TCP shares bottleneck B/W according to
  RTT
• May Not provide enough B/W for streaming apps

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Example Situation
Low RTT
Most Bandwidth!
Med. RTT
High RTT
Congestion
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Talk Outline

• Motivation Goals
• Our Approach
• Experimental Results
• Related Work
• Conclusion

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Our Approach

• We developed a receiver-based bandwidth sharing
  system (BWSS) for TCP INFOCOM 2003
• Key Idea Break fairness among TCP flows to allow
  user-specified B/W allocation
• Approach Limit throughput of low-priority
  connections to provide B/W for high-priority ones
• Ensures full utilization of access link
• Doesnt require changes to TCP/senders or
  infrastructure

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BWSS Overview
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Target Rate Allocation Subsystem
T1

• Some apps need minimum guaranteed rate(video),
  others dont (ftp)
• User assigns each flow
• Priority, minimum rate and weight
• Bandwidth allocation algorithm
• Satisfy minimum rate in decreasing order of
  priority
• Remaining B/W shared according to weight

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Flow Control System (FCS)
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s Calculation Subsystem
R1
s Si Ti
RN

• Goal Choose s to maximize link utilization. U
  Si Ri (s)
• Approach Use increase/decrease in measured
  throughput to guide increase/decrease of s

T2 ? R2
T2 R2
T1 R1
T2 R2
Link Capacity
T1 R1
U
s
W1
W2
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Talk Outline

• Motivation Goals
• Our Approach
• Experimental Results
• Related Work
• Conclusion

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Experimental Setup
RUDE
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Experimental Details
User Level App ? easy to deploy
Invisible to Apps
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TCP vs BWSS Internet Experiments
BWSS
TCP

• Video streamed at 496Kbps
• Congestion on access link from 30s to 60s
• Standard TCP not good enough during congestion

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BWSS Reduces Required Pre-Buffering

• BWSS provides 4X reduction in pre-buffering over
  standard TCP

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SureStreamTM Experimental Setup
RUDE
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RealVideo SureStreamTM Internet Experiments
TCP w/ BWSS
Despite congestion, video streams at steady rate.

Poor streaming quality
TCP

• Takeaway standard TCP not good enough for
  streaming

• Video encoded at 450Kbps, 350Kbps, 260Kbps
  64Kbps
• Congestion on access link from 60s to 100s
  (320Kbps)

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RealVideo SureStreamTM Internet Experiments
UDP
TCP w/ BWSS
UDP SureStream unable to stream at 450KBps till
after congestion
Constant streaming at 450Kbps

• Takeaway BWSS can break fairness among flows
  locally, and provide additional B/W for video
  apps.

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Related Work TCP Streaming

• Network-Based Approaches
• Receiver-based Delay Control (RDC) NOSSDAV 2001
• receivers delay ACK packets based on router
  feedback
• Mimic a CBR connection
• End-Host Approaches
• Time-lined TCP (T-TCP) ICNP 2002
• TCP Real-Time Mode (TCP-RTM) ICNP 2002
• Must modify both sender receiver to allow
  skipping late packets

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Conclusions

• BWSS allows flexible allocation of link B/W
• Breaks fairness among TCP flows locally in
  manner unavailable to TCP-Friendly UDP protocols
• BWSS enables efficient video streaming over TCP
  to bandwidth-limited receivers
• Better performance than standard TCP
• In some cases, better performance than
  congestion-aware UDP
• Future Work Incorporating UDP flows

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Questions?