1. Peer-to-peer: past, present, future
Cristina Cărbunaru
16 February 2011

2. Peer-to-peer
 Internet today
◦ Large number of hosts
◦ Large amount of content
 Significant challenges for traditional
client-server architectures
 Make use of the inter-connectivity of
the nodes in the Internet
◦ Alleviate the load from servers
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3. Client-server vs. P2p
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4. The Peer
 Double function:
◦ Client - consumer
◦ Server - producer
 Incentives to offer service, not just
benefit from service
 More peers means more capacity
added to the system
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5. P2p Goals
 Reduced central control
 Heterogeneity
 Flat topology
 Autonomy
 Fault resilience
…
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6. History
 File sharing applications
◦ 1999: Napster
◦ Gnutella, Kazaa, Freenet
◦ 2001: BitTorrent (Bram Cohen)
◦ Multiple variations of p2p programs
 Nowadays:
◦ File sharing – among individual users or in
the data centers
◦ Media streaming – on-demand or live content
◦ Communication – Skype!
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7. The beginnings: Napster
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8. BitTorrent
Seed
Tracker
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9. BitTorrent
Seed
Leecher
Tracker
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10. BitTorrent
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11. BitTorrent
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12. BitTorrent
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13. BitTorrent
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14. BitTorrent
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15. BitTorrent
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16. BitTorrent
Free-rider
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17. Swarm Behavior
 Incentive mechanisms
◦ Why offer service?
 Flash crowd
◦ Large number of peers choke the
performance
 Steady state
◦ Number of peers stays constant over time
◦ Easy to predict performance
 Lifetime
◦ When and why is the torrent dying?
 ...
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18. Peer Behavior
 Free riding
◦ Evaluate performance loss
◦ Methods to prevent
 Best results with minimum of effort
◦ Cheating, but not exactly
 Clustering of peers
◦ Peers download/upload to similar bandwidth
peers
 Security of content
◦ Malicious data
 Connectivity
◦ NAT boxes
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19. Approaches
 Measurement
◦ Real swarms
◦ Experimental platforms: PlanetLab, EmuLab
 Simulation
 Modeling
 Proposing new p2p protocols that solve
different problems
◦ Proportional upload bandwidth: PropShare
◦ Amount of data transferred: Avalanche
◦ Upload bandwidth allocation among peers to
get the best download speed: BitTyrant
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20. P2p in 2008/2009 (Ipoque study)
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21. Popularity
 Decreasing popularity for p2p file
sharing
◦ Packet filtering
◦ Packet inspection
◦ Lawsuit against Pirate Bay
◦ …
 One click file hosting services
(Rapidshare, Hotfile) become popular
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22. What to Research?
 Packet filtering
◦ Glasnost
 Hiding identity
◦ Tor
◦ Anonymous p2p
 Copyright issues
◦ Download might be legal in some
countries
◦ Upload is illegal
 …
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23. What’s Next?
 Increasing usage of p2p protocols in
other contexts:
◦ Media streaming, communication
◦ Inside the data centers
◦ Social networks
◦ Economics
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24. Future
 New technologies
◦ IPv6
◦ Mobile devices
 From computer-to-computer to
human-to-human
◦ commons-based peer production (Yochai
Benkler):
 Peer governance
 Peer property
 Peer distribution
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25. Conclusions
 Successful piece of research
◦ P2p transcended computer science
 Changed the way we share
◦ Files
◦ Knowledge
◦ Peer generated content
 P2p is here to stay!
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26. Questions?
Thank you!
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