BiToS: Enhancing BitTorrent for Supporting Streaming Applications

1
BiToS Enhancing BitTorrent for Supporting
Streaming Applications

• Aggelos Vlavianos, Marios Iliofotou,
• Michalis Faloutsos (From INFOCOM 2007)

2
Motivation

• Apply time sensitive function into
  BitTorrent(BT), which can distribution 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

3
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 handovernew
  protocol)

4
BiToS Approach
Remaining Windows
Small Windows

• a

Storing buffer
5
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

6
Simulation setting

• 4400 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) from Coolstreaming
• Average overall continuity index?

7
Simulation result (I)
Missing playback deadline Why not decrease
further? Since the flash crowd of peer at
beginning of simulation
8
Simulation result (II)
Use 5 min length video
Time for seeder stay in the network
9
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)

10
Improvement to be made (I)

• Dynamics of the seeder/leecher ratio
• Identify the event for triggering dynamic
  adaptation of p
• Further simulation and application to real BT
  system

11
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

12
BASS Architecture
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Simulation Result (I)
BASS reduce media server load 131 to 87kBps
(slope) less than half
14
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.

15
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?g
  vc2

16
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