Cmpe 494 PeertoPeer Computing

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Cmpe 494Peer-to-Peer Computing

• Anil Gürsel
• Didem Unat

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• Goals of P2P
• Cost sharing/reduction
• Improved scalability/reliability
• Resource aggregation and interoperability
• Increased autonomy
• Anonymity/privacy
• Dynamism
• Enabling ad-hoc communication and collaboration

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• P2P Models
• Pure P2P
• No central server exists. All peers have
  similar properties.
• Hybrid P2P
• Meta-data of a peer is learned from central
  server, then direct
• conneciton is established with peer.

(1) Initial communication with a server, e.g. to
obtain the location/identity of a peer (2) Direct
communication with a peer
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P2P Infrastructure Components
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P2P Algorithms
Flooded Requests Algorithm
Central Index Algorithm
Document Routing Algorithm
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P2P Systems

• Distributed computing
• - Desktop machines most often underutilized
• - Problem is divided into small parts
• - Peers return results to central server
• File sharing
• P2P Communication
• IM services, chat, online games Skype-voice
  over IP
• P2P platforms
• JXTA and .NET

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Distributed Computing

• Also called Grid computing
• Research and financial domain
• Computational Problems and Data Grids
• Simulations, Genome Project, Cancer Research,
  Weather Forecast
• Projects Globus, LCG, SETI_at_home, See-Grid,
  Needit
• scales well for SPMD problems
• supercomputing for a low price
• Checkpoints and Virtual Organizations
• Hard to parallelize the problem
• Security and Resource Management

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File Sharing

• Napster
• mp3 file sharing and searching service
• centralized directory model
• Gnutella
• purely distributed system
• queries are sent to the peers they know,
  TTL
• if a query match is found then the file is
  sent
• - flooding is not efficient, downloads entire
  file from a single peer. No checkpoint.

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File Sharing-BitTorrent

• Hybrid p2p solution
• More collaborative communities
• Low rate of freeriding
• Key concepts trackers and torrent
• While downloading, upload to others
• Age and share ratio

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P2P Platforms

• JXTA and .NET
• JXTA introduced by Sun, 2001, open source
• - p2p protocols
• - cell phones, PDA, PC can connect and
  communicate
• - enables collaboration, sharing compute
  services
• - developers can create new p2p applications,
  JXTA
• provides necessary infrastructure for them
• - supports multiple platforms and languages,
  micro-
• devices to servers
• - uses Java and XML

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JXTA Virtual Network
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Summary

• Decentralization
• Scalability
• Anonymity
• Self-Organization
• Cost of Ownership
• Performance
• Security
• Transparency and Usability