impact of incentives in bittorrent by jenny liu and seth cooper
TRANSCRIPT
![Page 1: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/1.jpg)
Impact of Incentives in BitTorrent
By Jenny Liu and Seth Cooper
![Page 2: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/2.jpg)
Peer to Peer Networks
• Multiple independent peers connect to share resources with each other
![Page 3: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/3.jpg)
Incentives
• But what reason does one peer have to share its resources with another?
![Page 4: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/4.jpg)
Incentives
• Does a peer need something in return?
![Page 5: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/5.jpg)
Incentives
• Or is simple altruism enough?
![Page 6: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/6.jpg)
BitTorrent
• Torrent file directs peers to a tracker, which helps to coordinate peers
Torrent
Tracker
![Page 7: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/7.jpg)
BitTorrent
• Initial peer, known as a “seed,” begins with the complete file.
Torrent
Tracker Seed
![Page 8: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/8.jpg)
BitTorrent
• Peers trade pieces of the file amongst themselves, uploading pieces to the peers they are downloading the fastest from. When a peer finishes, it becomes a new seed.
Torrent
Tracker Seed
![Page 9: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/9.jpg)
Motivation
• Other P2P networks (Napster, Kazaa) have become successful relying on altruism alone.
![Page 10: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/10.jpg)
Motivation
• It is often claimed that freeloading on P2P networks is a problem, and many attempts have been made to find an effective incentive, but is one necessary?
![Page 11: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/11.jpg)
Motivation
• How effective is BitTorrent? Are incentives necessary? How do greedy peers affect the network? Are incentives an unnecessary overheard?
![Page 12: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/12.jpg)
System
• Modify BitTorrent source to remove incentives, and compare efficiency with unmodified BitTorrent
![Page 13: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/13.jpg)
System
• Assign each peer a strategy: greedy or altruistic.
![Page 14: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/14.jpg)
Metrics
• Client side: average download time
![Page 15: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/15.jpg)
Metrics
• Server side: percent of unicast
![Page 16: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/16.jpg)
Trials
• Measure data from several trials of one seed distributing a file to a set of peers. Start with a default network setting and vary parameters to see their effect on the two types of networks.
Seed
![Page 17: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/17.jpg)
Trials
• We varied: delay between peer connections.
![Page 18: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/18.jpg)
Trials
• We varied: minimum number of uploads for each peer.
![Page 19: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/19.jpg)
Results
0
5
10
15
20
25
30
35
40
45
50
0 2 4 6 8 10
Tim
e to
com
plet
e do
wnl
oad
Delay coefficient
Effect of delay coefficient on time to complete download
vanillano incentive
0
20
40
60
80
100
0 2 4 6 8 10
Per
cent
of u
nica
st
Delay coefficient
Effect of delay coefficient on percent of unicast
vanillano incentive
ideal
0
5
10
15
20
25
30
35
40
45
50
1 2 3 4 5 6 7Ti
me
to c
ompl
ete
dow
nloa
dMinimum number of uploads
Effect of minimum number of uploads on time to complete download
vanillano incentive
0
20
40
60
80
100
1 2 3 4 5 6 7
Per
cent
of u
nica
st
Minimum number of uploads
Effect of minimum number of uploads on percent of unicast
vanillano incentive
ideal
• Not much difference.
![Page 20: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/20.jpg)
Trials
• We varied: total number of peers.
![Page 21: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/21.jpg)
Results
0
5
10
15
20
25
30
35
40
45
50
2 4 6 8 10 12 14 16
Tim
e to
com
plet
e do
wnl
oad
Number of peers
Effect of number of peers on time to complete download
vanillano incentive
• Number of peers has an effect on download time when the incentive is removed.
![Page 22: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/22.jpg)
Trials
• We varied: percentage of greedy peers.
![Page 23: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/23.jpg)
Results
0
20
40
60
80
100
0 20 40 60 80 100
Per
cent
of u
nica
st
Percentage of greedy peers
Effect of percentage of greedy peers on percent of unicast
vanillano incentive
ideal
• Percentage of greedy peers has an effect on both metrics when the incentive is removed.
0
50
100
150
200
0 20 40 60 80 100
Tim
e to
com
plet
e do
wnl
oad
Percentage of greedy peers
Effect of percentage of greedy peers on time to complete download
vanillano incentive
![Page 24: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/24.jpg)
Trials
• We varied: size of network and tried different percentages of greedy hosts
![Page 25: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/25.jpg)
Results
• As the network gets bigger, a larger percentage of greedy hosts can be supported
0
50
100
150
200
0 20 40 60 80 100
Tim
e to
com
plet
e do
wnl
oad
Percentage of greedy peers
Effect of percentage of greedy peers on time to complete download
vanillano incentive
0
50
100
150
200
0 20 40 60 80 100Ti
m to
com
plet
e do
wnl
oad
Percent of greedy peers
Effect of percent of greedy peers on time to complete download
vanillano incentive
10 Peers 20 Peers
![Page 26: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/26.jpg)
Conclusions
• Q: How efficient is BitTorrent?
• A: Very.
![Page 27: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/27.jpg)
Conclusions
• Q: Are incentives necessary?
• A: It depends.
![Page 28: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/28.jpg)
Conclusions
• Q: How do greedy peers affect the network?
• A1: Not much. • A2: Not much up to a point. • A3: Quite a lot after that.
![Page 29: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/29.jpg)
Conclusions
• Q: Are incentives an unnecessary overhead?
A: No!
![Page 30: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/30.jpg)
Future Work
• Conduct experiments on more heterogeneous networks.
• Try UDP.
• Address other negative aspects of BitTorrent, such as content lifetime.
![Page 31: Impact of Incentives in BitTorrent By Jenny Liu and Seth Cooper](https://reader035.vdocuments.site/reader035/viewer/2022070404/56649f345503460f94c50c67/html5/thumbnails/31.jpg)
The End