Providing Controlled Quality Assurance in Video Streaming across the Internet

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Providing Controlled Quality Assurance in Video
Streaming across the Internet

• Yingfei Dong, Zhi-Li Zhang and Rohit Rakesh
• Computer Networking and Multimedia Research Group
  
• Dept. of Computer Science and Engineering
• University of Minnesota

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Motivations

• The Internet Service-Oriented Network
• Service Requirement End-to-End QoS
• Service Delivery System Content Distribution
  Networks
• On-Demand Large Stored Video Streaming
  
• --- High Bandwidth requirements
• Wide-Area Stored Video Delivery System
• Common Approach --- Proxy Server System

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Proxy Content Delivery Architecture
Proxy Server VPN
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Virtual Private Network(VPN)

• Network- Layer VPN
  not Leased-Lines, but Service Level Agreements,
• Coarse-grain average
• T3 VPN, 99.9 available, 120 ms average RTT
  monthly average
• No rate guarantee for individual flows
• No packet loss/delay guarantee
• Application-level Traffic Management is needed.

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System Constraints and Challenge

• Constraints
• Limited Buffer Space v.s. Huge Video Volume
  
• Streaming from central servers is required.
• Aggregate B/W v.s. Individual Flow Requirement
• Bandwidth management must be present.
• Stringent Timing v.s. No Delay/Loss Guarantee
• Reliably prefetching is necessary.
• Challenge
• Quality Assurance across Best-Effort Networks

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Outline

• Motivations and Background
• Staggered Two-Flow Streaming
• Control Bandwidth Sharing
• Conclusion and Current Work

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Objective and Approaches

• Controlled Quality Assurance in streaming on the
  best-effort Internet by exploiting
• Application Information, such as the priority
  structure in videos (frame-dependency), and flow
  rate
• Coarse-grain bandwidth assurance of VPN
• Storage / processing capacity of proxy servers

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Priority Structure in Videos

• Two flows in a video session
• A Reliable Flow for essential data (e.g., I
  frames)
• An Unreliable Flow for enhanced data (e.g., P/B)

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Segment and Staggered Delivery

• The Reliable Flow is one segment ahead

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Staggered Two-Flow Streaming

• Reliable Flow I-frame segments,
  prefetched and cached at proxy.
• Unreliable Flow P/B-frames segments,
  real-time delivery subject to adaptation when
  congestion in the soft VPN pipe.
• Merging both flows at Proxy Server, then send to
  clients

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Illustration
Competition!!
Prefetching Cache
Proxy Server
Central Server
best-effort VPN
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Interesting Issues

• Data Plane Issues
• Bandwidth Competition
• Unreliable-Flow Rate Adaptation
• Control Plane Issues
• Application-aware Resource Management
• e.g., Admission Control, VPN management,
  Video placement and migration
• Implementation Issues

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Application-Aware Controlled Bandwidth Sharing

• Stable and Predictable transport protocols
• Controlled TCP (cTCP)
• Application-aware throughput control
  A variant of TCP Reno using a simple TCP model
  to regulate the injection rate.
• Rate-Controlled UDP(rUDP)
• Generating Piece-wise CBR traffic Extending UDP
  on FreeBSD with a periodical injection mechanism
  limited by a leaky-bucket
• Both are implemented in FreeBSD kernel.

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TCP reliable but not fit to our setting

• Sliding Window (W) Injection Control
• W packets per RTT
• AIMD
• Fluctuation Greedily Increase,
  back off to half when loss
• Fairness regardless of flow
  requirements

Packet losses even when sufficient B/W
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cTCP a variant of TCP Reno

• Flow Target Rate TcTCP
• Target Window Size Wtarget
• using a simple TCP bandwidth model to limit the
  injection to the flow requirement
• If packet loss
• else

No slow-start. No packet losses when given
sufficient B/W.
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Two cTCP Flows v.s. Two TCP Flows
On a 64KBps link, the 1st flow with a target rate
13KBps starts 12 seconds earlier than the 2nd
flow with a target rate 27KBps

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Experimental Environment

• Controlled Testbed on FreeBSD4.1
• 3 PCs on a dedicated Gbps Ethernet switch
• A central server and a proxy server
• A bandwidth-and-delay control unit emulates a
  VPN pipe in between, running IP Dummynet
• Testing Video a 60-minute MPEG-2 video clip
• Target Rate of I frames, 52 KBps
• Target Rate of P/B frames, 200 KBps

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Multiple Sessions cTCP/rUDP v.s. TCP/rUDP
A video session of two flows (cTCP/rUDP or
TCP/rUDP)

• RXs in TCP or cTCP

• rUDP Losses

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Multiple Sessions (Arrival / Departure)
cTCP/rUDP v.s. TCP/rUDP

• C 5 1.1 Max_Rate
• Starting with 4 sessions
• Then, add one more
• Later, terminate two.
• Compare the variations of packet RXs and losses

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Summary of Controlled BW Sharing

• Practical quality assurance of the essential data
  over best-effort networks
• None / Low Packet Losses
• Stable, Predictable System Performance
• Providing chances for applying simple
  application-aware traffic management
• TCP-firendly do not grab BW from others
• Patent Pending

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Current and Future Work

• Quality Assurance issues in Service-Oriented
  Networks
• Scalability in data plane
• Aggregation at the levels of video, session, and
  flow.
• Network parameters sharing among sessions.
• Service-Oriented B/W Management in control plane
• Application-ware admission control
• Proxy Placement utilizing the topology info.
• Proxy Caching and Video Placement / Migration.
• High-Quality VOD on Cable Broadband Networks.