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BiToS: Enhancing BitTorrent for Supporting Streaming Application
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Aggelos Vlavianos, Marios Iliofotou,
Michalis Faloutsos (From INFOCOM 2007)
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Motivation Apply time sensitive function into BitTorrent(BT), which can distributi
on of time insensitive content. Minimize the change of BT mechanism to achieve this
To reduce start-up time To evaluate the video quality
To view the downloading video first (in highly polluted network) view-as-you-download service
Rarest first order V.S. playback smooth (playing order) Tunable between pure streaming and original BT
Three different piece selection mechanisms Only need to change this part in BT
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Motivation
BASS: BitTorrent Assisted Streaming System for Video-on-Demand Client will not download any data prior to the current playback time
Time constrained data stronger incentive with Tit-for-Tat peers will avoid to be Free-Riders
Use BT to handle live streaming, change the tracker entity and some parts of peer communication protocol (signal handover=new protocol)
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BiToS Approach
a
Small Windows
Storing buffer
Remaining Windows
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BiToS Approach
Probability p to download a piece in the High Priority set (p can be adjust to adapt different condition)
Probability (1-p) to download a piece in the Remaining Pieces set
One more function to determine if the piece can be downloaded on time or not Compare the expected playback time and minimum time
Adaptation of probability p can be triggered by playback deadline missing
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Simulation setting
4:400 for Seed and Leechers Flash crowds at the beginning 10 minutes length, video quality 500Kbps Download/Upload rate 500/500Kbps Other use BT default settings (256Kb per piece?) No dynamic adaptation of probability p No peer dynamic Only one performance metrics continuity index (CI) f
rom Coolstreaming Average overall continuity index?
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Simulation result (I)
Missing playback deadlineWhy not decrease further?Since the flash crowd of peer at beginning of simulation
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Simulation result (II)
Time for seeder stay in the network
Use 5 min length video
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Improvement to be made (I)
Analysis of Probability p is not detail enough How to trigger the dynamic How to set the value
Probability can be a function of buffer status or time
No study effect of buffer length Simple theory to explain why ~8% total file as
high priority set is optimal (High CI)
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Improvement to be made (I)
Dynamics of the seeder/leecher ratio Identify the event for triggering dynamic adap
tation of p Further simulation and application to real BT
system
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BitTorrent Assisted Streaming System (BASS)
BitTorrent assisted the system only Media server is the main support (Maybe) Simply adding two systems together for BASS
From the media server, BASS downloads pieces in-order, and skip pieces are downloading/ downloaded/ expected to finish download before playback deadline
BitTorrent are directly used for streaming application without any modification
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BASS Architecture
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Simulation Result (I)
BASS reduce media server load 131 to 87kBps (slope) ~less than half
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Simulation Result (II)
The average required bandwidth on the media server can be decreased by up to 34% when using BASS compared with pure media server case
Average client waiting time is decreased by 27% compared to the pure media server case.
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Existing BT application for streaming
Current BT application for streaming: FoxTorrent
Streaming Fast Delivery: Watch video and listen to audio as it downloads.
Open source FoxTorrent, Firefox extension that lets users stream torrents as they download, from their web browser
http://www.foxtorrent.com/ http://groups.google.com/group/foxtorrent/topics?gvc=
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VoD with BT-assist
Following BT mechanisms might need to be re-design/re-construct
Peer selection Piece selection
Pull based Push and Pull based