Peer-to-peer: past, present, future

Cristina Cărbunaru16 February 2011

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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Client-server vs. P2p

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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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P2p Goals Reduced central control Heterogeneity Flat topology Autonomy Fault resilience …

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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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The beginnings: Napster

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BitTorrent

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Tracker

Seed

BitTorrent

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Leecher

Seed

Tracker

BitTorrent

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BitTorrent

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BitTorrent

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BitTorrent

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BitTorrent

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BitTorrent

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BitTorrent

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Free-rider

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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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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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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P2p in 2008/2009 (Ipoque study)

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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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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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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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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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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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Questions?

Thank you!

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