Improving BitTorrent: A Simple Approach

1
Improving BitTorrent A Simple Approach

• Author Alix L.H. Chow, Leana Golubchik, Vishal
  Misra
• Presenter Chen Chih-Ming

2
Outline

• Introduce BT scheme
• Sample
• Approaches
• Result
• Conclusion
• Comment

3
BitTorrent

• P2P
• Role
• Seed
• Leacher
• Sharing Policy
• Unchocked algorithm
• Seeding algorithm

4
Free-Rider

• Leechers
• No upload
• Chance
• Optimistic unchoking mechanism
• Seeding mechanism

5
Stat of Art

• Fairness
• Robustness
• Performance
• Seeding behavior!

6
Sample
Class Fraction Download Capacity Upload Capacity
Contributing 80 5000kbps 512kbps
Free-Riders 20 5000kbps 0kbps
7
Approaches

• Get rid of them
• Slow them down
• Contributing node use tit-for-tat to punish them
• But seed?

8
Approaches cont.

• Who does need seeds?
• the poorest
• the richest!
• Scheme
• The Furthest one
• Thresold-based

9
Experiment

• Simulator
• Implements
• Original
• Optimized
• Approaches
• Sort-based
• T 20
• T 40

10
Settings
Filesize 500MB(2000 Chunks, 256KB each)
Simulation Time 24 hours (6 hours warm up time)
Avg. node inter-arrival time(1/lamda) 1 min
Peer Set size 80
Leecher Unchokings 4 Regular 1 Optimistic
Seed Unchokings 5
Class Fraction Download Capacity Upload Capacity
Slow 40 1500kbps 128kbps
Fast 40 5000kbps 512kbps
Free-Riders 20 1500kbps 0kbps
11
Results
12
Advantage

• Start faster
• Free riders may contribute themselves

13
Fail Scenario

• Too few seeds
• Too many seeds

14
Exploit

• Large View exploit
• Lie to one seed
• Lie to many seed
• Mulitple IP

15
Conclusion

• Degrade free riders performance
• Improving the performance of contributing leechers

16
Comment

• Easy approach
• Effective results
• Undefined quantity
• Too Few experiment
• File size
• Seed capacity
• Weak for lying exploit (Future work)
• Only simulation (Future work)

17
Thank you again

• Bye