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 Peer-to-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

• 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

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

TrackerWeb Server

.torr

ent

Overview – system components

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker

Get-announce

Web Server

Overview – system components

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker

Response-peer list

Web Server

Overview – system components

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker

Shake-hand

Web Server

Shake-hand

Overview – system components

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker

pieces

pieces

Web Server

Overview – system components

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker

piecespieces

pieces

Web Server

Overview – system components

Web page with link to .torrent

A

B

C

Peer

[Leech]

Downloader

“US”

Peer

[Seed]

Peer

[Leech]

Tracker

Get-announce

Response-peer list

piecespieces

pieces

Web Server

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 worksPaper Method Data set Research

DifferentiationYV_INFOCOM04 Model + Trace Trace log of 150-

200 torrents trackers

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 48 days tracker trace and 10 days ISP traffic (50 tracker sites and 3k peers)

Performance across multi-torrents, BT limitation found from traces.

BHP_INFOCOM06 Comprehensive simulation

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 multi-seeds

– 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)