bittorrent · levin, et al. “bittorrent is an auction: analyzing and improving bittorrent’s...
TRANSCRIPT
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BitTorrent Overview
peer
![Page 3: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/3.jpg)
BitTorrent Overview
peertracker
![Page 4: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/4.jpg)
BitTorrent Overview
130.136.254.21130.136.254.22171.66.3.182128.31.1.11
128.83.122.180128.232.103.202
155.98.35.4128.163.142.20
...
peertracker
![Page 5: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/5.jpg)
BitTorrent Overview
peer
leechers
![Page 6: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/6.jpg)
BitTorrent Overview
peer
neighbors
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BitTorrent Overview
peer
neighbors
![Page 8: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/8.jpg)
BitTorrent Overview
peer
neighbors
![Page 9: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/9.jpg)
BitTorrent Overview
peer
neighbors seeders
![Page 10: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/10.jpg)
Phases of BitTorrent
0%
100%
% D
ownl
oade
d
Bootstrapping: Getting the first pieces
Steady-state: Trading with peers
End-game: Getting the last pieces
![Page 11: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/11.jpg)
Phases of BitTorrent
0%
100%
% D
ownl
oade
d
Bootstrapping: Getting the first pieces
End-game: Getting the last pieces
assumption: peers have pieces to trade with other peers
Steady-state: Trading with peers
![Page 12: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/12.jpg)
Steady-state
in steady-state, a BitTorrent peer uploads to and
downloads from different neighbors
![Page 13: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/13.jpg)
Steady-state
in steady-state, a BitTorrent peer uploads to and
downloads from different neighbors
![Page 14: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/14.jpg)
Steady-state
in steady-state, a BitTorrent peer uploads to and
downloads from different neighbors
how does he decide who to upload to, how much to
upload, etc.?
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Steady-stateRound t
divide protocol into rounds. peers that upload the most to us in round t get uploaded to in round t+1
![Page 16: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/16.jpg)
Steady-stateRound t
divide protocol into rounds. peers that upload the most to us in round t get uploaded to in round t+1
Round t+1
![Page 17: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/17.jpg)
BitTorrent’s Unchoker
13
10
97
12
4
15
Round t
![Page 18: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/18.jpg)
BitTorrent’s Unchoker
13
10
97
12
4
15
Round t
![Page 19: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/19.jpg)
BitTorrent’s Unchoker
13
10
97
12
4
15
Round t
10
10
10
10
Round t+1
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BitTorrent’s Unchoker
20?
15
13
10
12
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BitTorrent’s Unchoker
20?20
15
13
10
12
![Page 22: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/22.jpg)
BitTorrent’s Unchoker
20?20
15
13
10
12
![Page 23: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/23.jpg)
BitTorrent’s Unchoker
20?
10
10
10
10
![Page 24: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/24.jpg)
BitTorrent’s Unchoker
11?
15
13
10
12
![Page 25: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/25.jpg)
11
BitTorrent’s Unchoker
11?
15
13
10
12
![Page 26: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/26.jpg)
11
BitTorrent’s Unchoker
11?
15
13
10
12
![Page 27: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/27.jpg)
10
10
10
10
BitTorrent’s Unchoker
11?
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10
10
10
10
BitTorrent’s Unchoker
11?
Best strategy: Come in last
peers do not have incentive to give as much as possible
Piatek, et al. “Do Incentives Build Robustness in BitTorrent?”. NSDI 2007
![Page 29: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/29.jpg)
BitTorrent’s Unchoker
42?
15
13
10
12
![Page 30: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/30.jpg)
BitTorrent’s Unchoker
15
13
10
12
14 14 14
![Page 31: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/31.jpg)
BitTorrent’s Unchoker
15
13
10
12
14 14 14141414
![Page 32: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/32.jpg)
BitTorrent’s Unchoker
15
13
10
12
14 14 14141414
![Page 33: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/33.jpg)
BitTorrent’s Unchoker
14 14 14
10
10
1010
![Page 34: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/34.jpg)
BitTorrent’s Unchoker
14 14 14
10
10
1010
Sybil Attack: Create additional identities to
subvert the system
![Page 35: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/35.jpg)
PropShare Unchoker
13
10
97
12
4
15
Round t
Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008
![Page 36: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/36.jpg)
PropShare Unchoker
13
10
97
12
4
15
Round t
Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008
![Page 37: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/37.jpg)
PropShare Unchoker
13
10
97
12
4
15
Round t
Total: 70
Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008
![Page 38: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/38.jpg)
PropShare Unchoker
13
10
97
12
4
15
Round t
Total: 70
13/70
10/70
12/70
15/70
Round t+1
4/70
9/70
7/70
Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008
![Page 39: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/39.jpg)
PropShare Unchoker
20?
50
![Page 40: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/40.jpg)
PropShare Unchoker
20?
2050
![Page 41: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/41.jpg)
PropShare Unchoker
20?
2050
Total: 70
![Page 42: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/42.jpg)
PropShare Unchoker
20?Total: 70
50/70 20/70
![Page 43: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/43.jpg)
PropShare Unchoker
11?
50
![Page 44: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/44.jpg)
PropShare Unchoker
11?
1150
![Page 45: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/45.jpg)
PropShare Unchoker
11?
1150
Total: 61
![Page 46: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/46.jpg)
PropShare Unchoker
11?Total: 61
50/61 11/61
![Page 47: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/47.jpg)
PropShare Unchoker
11?Total: 61
50/61 11/61
Upload Less →Receive Less →
Incentive to Upload More
![Page 48: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/48.jpg)
PropShare Unchoker
2050
5 5
55
![Page 49: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/49.jpg)
PropShare Unchoker
2050
Total: 70
5 5
55
![Page 50: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/50.jpg)
PropShare Unchoker
Total: 70
50/70 20/70
5 5
55
![Page 51: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/51.jpg)
PropShare Unchoker
Total: 70
50/70 20/70
5 5
55
+ + + =
5 5 5 520
![Page 52: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/52.jpg)
PropShare Unchoker
Total: 70
50/70 20/70
5 5
55
+ + + =
5 5 5 520
PropShare is Sybil-proof
![Page 53: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/53.jpg)
Steady-state Results
• BitTyrant and PropShare are both faster than BitTorrent
• For different reasons
• PropShare performs comparably to BitTyrant
• PropShare does not suffer from a tragedy of the commons
• BitTyrant does
![Page 54: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/54.jpg)
Phases of BitTorrent
0%
100%
% D
ownl
oade
d
Bootstrapping: Getting the first pieces
Steady-state: Trading with peers
End-game: Getting the last pieces
![Page 55: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/55.jpg)
Phases of BitTorrent
0%
100%
% D
ownl
oade
d
Steady-state: Trading with peers
End-game: Getting the last pieces
assumption: peers have nothing to give to other peers
Bootstrapping: Getting the first pieces
![Page 56: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/56.jpg)
Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
![Page 57: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/57.jpg)
Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
![Page 58: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/58.jpg)
Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
![Page 59: BitTorrent · Levin, et al. “BitTorrent is an Auction: Analyzing and Improving BitTorrent’s Incentives”. SIGCOMM 2008. PropShare Unchoker 13 10 9 7 12 4 15 Round t Total: 70](https://reader036.vdocument.in/reader036/viewer/2022070109/604309eec116956cc34309a0/html5/thumbnails/59.jpg)
Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
exploit: always asked to be optimistically unchoked (i.e., never upload)
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Optimistic Unchokingreserve a portion of bandwidth to give freely to other peers
(presumably new peers)
exploit: always asked to be optimistically unchoked (i.e., never upload)
tragedy of the commons: system will collapse if everyone does this
Locher, et al. “Free Riding in BitTorrent is Cheap”. HotNets, 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
no incentive to repeatedly ask for unchoking, but wastes system resources
Li, et al. “BAR Gossip”. OSDI 2006
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Junk Updatesforce peers to upload useless data
no incentive to repeatedly ask for unchoking, but wastes system resources
Li, et al. “BAR Gossip”. OSDI 2006
can we put new peers to work doing something useful?
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TBSLevin, et al.
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TBSLevin, et al.
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TBSLevin, et al.
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TBS
both and
get pieces from
Levin, et al.
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TBSLevin, et al.
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TBSLevin, et al.
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TBSLevin, et al.
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TBS
can send junk
problem:
Levin, et al.
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TBS
or nothing at allcan send junk
problem:
Levin, et al.
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TBS
Solution: Encryption
or nothing at allcan send junk
problem:
Levin, et al.
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TBSLevin, et al.
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TBSLevin, et al.
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TBScorrect?correct? Levin, et al.
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TBSLevin, et al.
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Bootstrapping Summary
• Bootstrapping is not a very large part of the download. Even so, it can be exploited
• A better bootstrapping mechanism has potential to yield better performance throughout the download
• Moreover, it can be used whenever a peer becomes uninteresting, not just in the bootstrapping phase
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Phases of BitTorrent
0%
100%
% D
ownl
oade
d
Bootstrapping: Getting the first pieces
Steady-state: Trading with peers
End-game: Getting the last pieces
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Phases of BitTorrent
0%
100%
% D
ownl
oade
d
Bootstrapping: Getting the first pieces
Steady-state: Trading with peers
assumption: not many peers are mutually interesting
End-game: Getting the last pieces
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Strategic Piece Revelation
Round t
Goal: Be as interesting as possible to lots of peers
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Strategic Piece Revelation
Round t
Goal: Be as interesting as possible to lots of peers
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Strategic Piece Revelation
Round t
Goal: Be as interesting as possible to lots of peers
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Strategic Piece Revelation
Round t+1
Goal: Be as interesting as possible to lots of peers
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Strategic Piece Revelation
Round t+1
Goal: Be as interesting as possible to lots of peers
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Strategic Piece Revelation
Round t
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Strategic Piece Revelation
Round t
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Strategic Piece Revelation
Round t
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Strategic Piece Revelation
Round t
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Strategic Piece Revelation
Round t+1
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Strategic Piece Revelation
Round t+1
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Strategic Piece Revelation
Round t+1
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Strategic Piece Revelation
Strategically reveal pieces → Peers are interested in me
longer
Round t+1
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Peer Selection
• Before our download even starts, a BitTorrent client gets a set of peers from the tracker.
• During the download, the peer figures out the “best” of this set
• What if we could decide which peers would be best without trading with them first?
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Peer Selection
• Measuring link characteristics is sometimes seen as a threat, and doesn’t scale
• Many measurement systems require a “map” of the Internet, which is hard to obtain
• Network coordinate systems don’t require a map, but are complicated and don’t always work
• Could try simple things (use peers in our ISP, e.g.), but it’s not clear that these work either
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Summary
• BitTorrent is a large system; lots of things to tweak
• Bootstrapping, steady-state, end-game phases
• Peer selection
• Not all strategies are fair
• A combination of techniques (from various phases) would probably result in an extremely fast client