Transcript The BitTorrent protocol

A survey of BitTorrent study
Jian Liang
EL933
Prof. Yong Liu
Surveyed paper
• Service Capacity of Peer to Peer Networks (INFOCOM 2004)
X. Yang, G. Veciana
• Modeling and Performance Analysis of Bit Torrent-Like Peerto-Peer Networks (SIGCOMM 04) D. Qiu, R. Srikant
• The Bittorrent P2P File-sharing System: Measurements and
Analysis (IPTPS 2005) J. Pouwelse, P.Garbacki, D. Epema,
H. Sips
• Measurements, Analysis, and Modeling of BitTorrent-like
Systems (IMC 2005) L. Guo, S. Chen, Z. Xiao, E. Tan, X.
Ding, and X. Zhang
• Analyzing and Improving BitTorrent Performance (INFOCOM
2006) A. Bharambe, C. Herley and V Padmanabhan
Outline
•
•
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•
•
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•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument
Current development of BitTorrent
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – system components
Tracker
Web Server
C
A
Peer
Peer
[Leech]
B
Downloader
Peer
“US”
[Leech]
[Seed]
Overview – BT features
• Temporal one torrent community (no
across torrents communication).
• File/pieces/blocks. Content trade is piece
based, while transfer is block based.
Partial pieces can not be uploaded.
Overview – BT features
• Peer selection- Fit-for-Tat (download
speed based) “Interest”/”chock”/”unchock”
• Piece selection - Local Rarest First (not
global rarest)
Outline
•
•
•
•
•
•
•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument
Current development of BitTorrent
Research focus
• Generic network performance
– Traffic volume, download/upload throughput, uplink
utilization, peer behavior, service capacity,
• Incentives
– Fairness, peer game
• Robustness
– Website availability, peer workload, content integrity.
• Limitation and improvement
Outline
•
•
•
•
•
•
•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument of their works
Current development of BitTorrent
Methodology
• Passive ways
– (tracker log, torrent website monitor, traffic
capture)
• Active ways
– Join the BT network to monitor peer
performance
• Simulation
• Modeling
Outline
•
•
•
•
•
•
•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument of their works
Current development of BitTorrent
Compare of these five works
Paper
Method
Data set
YV_INFOCOM04
Model + Trace
Trace log of 150200 torrents
trackers
Research
Differentiation
Service capacity,
scalability of flash
crowd
QS_SIGCOMM04
Model + simulation
+ little trace
3 days trace from
one torrent tracker
User evolution, peer
game
PG_IPTPS05
Trace
8 months trace
from website, peer
traffic and tracker
Torrent website
availability, content
integrity
GCXTDZ_IMC05
Trace + model
Performance across
multi-torrents, BT
limitation found from
traces.
BHP_INFOCOM06
Comprehensive
simulation
48 days tracker
trace and 10 days
ISP traffic (50
tracker sites and
3k peers)
None
Fairness, uplink
utilization,
improvement
Outline
•
•
•
•
•
•
•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument
Current development of BitTorrent
Interesting results
•
YV_INFOCOM04
–
Exponential growth of
service capacity in
initial flash crowd
–
For less popular torrent
(<50 peers), the
performance is quite
unpredictable
Interesting results
• QS_SIGCOMM04
– Purpose a good BT fluid model and matches
their simulation result well.
– No surprising results yet.
Interesting results
• PG_IPTPS05
– The arrival processes
of peers are not
Poisson assumed by
SIGCOMM04 paper.
– Power law
relationship btw peer
speed and # peers
Interesting results
• PG_IPTPS05
– The availability of
centralized supporting
system is bad
– # of seeds after 10 days
is not accurate predictor
for content life time, one
single seed can be up
for long period of time.
Interesting results
•
PGES_IPTPS05
– Centralized moderation seems very effective
in removing fake and corrupted files. 5k of
8k torrent uploaded by 20 moderators daily.
– Donated resource for meta-data entail
integrity and privacy risks without control.
Interesting results
• GCXTDZ_IMC05
– Exponentially decreasing peer
arrival rate, lack of seeds make
service availability poor quickly
after flash crowd.
– The leecher download speed at
different time stages is highly
diverse.
Interesting results
• GCXTDZ_IMC05
– BT can provide unfair services.
Peer contribution ratio decrease
with its downloading speed
increase.
– The probability for a peer to abort
downloading voluntarily is
independent of its speed and
downloading progress.
Interesting results
• GCXTDZ_IMC05
– The life spans of torrent is
btw 30-300 hours with
average 8.5 days; average
population of a torrent is
only about 102 peers.
– Seeding time is average as
8.42 hours
Interesting results
• BHP_INFOCOM06
– The uplink utilization close
to 100%
– Workload of seeds
increase slowly during
flash crowd
Interesting results
• BHP_INFOCOM06
– Single seed utilization
outperforms that of multiseeds
– The more concurrent
upload, the less uplink
utilization
Interesting results
• BHP_INFOCOM06
– For low bandwidth peers
with small neighbors,
random block exchange
outperform LRF
– But LRF outperform
random block exchange in
term of # interesting
connections
Interesting results
• BHP_INFOCOM06
– Block-level TFT outperform
download speed based
TFT in term of fairness
– Quick BW estimation help
archive optimal utilization
Interesting results
• BHP_INFOCOM06
– Bandwidth-matching tracker policy further improve both
utilization and fairness
Outline
•
•
•
•
•
•
•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument
Current development of BitTorrent
Argument
• INFOCOM06 :
– the simulation does not consider user control
of their uplink/downlink (BitComet enable
uplink speed limits)
– Tradeoff of the improvement ideas
– Bandwidth measure overhead is ignored
– Bandwidth clustering helps but is that violation
of Internet ethics by separating different
capable users?
Outline
•
•
•
•
•
•
•
Overview of BitTorrent
Research interests covered
Methodology on BT study
Compare of these 5 papers
Interesting facts reflected in these works
Argument
Current development of BitTorrent
Current BT development
• DHT enabled peer search (BitComet,
Bitsprite)
• Decentralized torrent search (eXeem)
• BT like Content delivery system (VOD,
IPTV)