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Jay Sheth

P2P Basics. Jay Sheth CE, UMBC. Jay Sheth. Jay Sheth. P2P Agenda. What is P2P Why P2P Components and algorithms Characteristics Different P2P systems Future Work. Jay Sheth. What is P2P ?. Peer is a entity that has attributes similar to other entities in system

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Jay Sheth

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  1. P2P Basics Jay Sheth CE, UMBC Jay Sheth Jay Sheth

  2. P2P Agenda • What is P2P • Why P2P • Components and algorithms • Characteristics • Different P2P systems • Future Work Jay Sheth

  3. What is P2P ? • Peer is a entity that has attributes similar to other entities in system • P2P is a technology and not a protocol • Process whereby computers trade information between each other without • having to pass the information through a centrally controlled server • Sharingof computer resources (information, processing) and services by • direct exchange between systems Jay Sheth

  4. What is P2P ? Jay Sheth Jay Sheth Jay Sheth

  5. Why P2P ? • Scalability increases by avoiding dependency on centralized points • Eliminates the need of costly infrastructure by enabling direct communication • among clients (cost sharing/reduction) • Enabling resource aggregation Jay Sheth Jay Sheth Jay Sheth

  6. Components Tools Applications Services Application-specific Class-specific Scheduling Meta-data Messaging Management Resource aggregation Robustness Security Reliability Group Management Discovery Locating, routing Communication Communication Jay Sheth Jay Sheth Jay Sheth

  7. Algorithms • Centralized directory model • Index : All peers publish information about the content they offer for sharing • Napster Jay Sheth Jay Sheth Jay Sheth

  8. Algorithms • Flooded requests model • - Pure P2P model • - Broadcast to all nodes • Gnutella Jay Sheth Jay Sheth Jay Sheth

  9. Algorithms • Flooded requests model modified Jay Sheth Jay Sheth Jay Sheth

  10. Algorithms • Document routing model • - Very efficient for large global communications • - Difficult to implement • - Islanding problem • - Freenet Jay Sheth Jay Sheth Jay Sheth

  11. Characteristics • Decentralization • Centralized systems • - Ideal for some applications • - Bottlenecks • - Inefficient use of resources • - Expensive to setup • - Hard to maintain • Decentralized systems • - Fully decentralized is difficult in practice • - Hybrid approach Jay Sheth Jay Sheth Jay Sheth

  12. Characteristics • Scalability • - Immediate benefit of decentralization • - At expense of performance guarantee • - Hybrid approach • - E.g. Napster : Users to directly download music files • Some operations, files centralized Jay Sheth Jay Sheth Jay Sheth

  13. Characteristics • Anonymity • - Receiver • Multicasting (underlying network should support multicast) • E.g. Gnutella • - Sender • Covert paths Jay Sheth Jay Sheth Jay Sheth

  14. Characteristics • Self-Organization • - Scaling results in increase in probability of failures • - Requires self-maintenance, self-repair of systems • - Costly to have dedicated equipment, hence distributed • E.g. OceanStore, self-organization applied to location • and routing infrastructure Jay Sheth Jay Sheth Jay Sheth

  15. Characteristics • Cost of Ownership • - Cost of owning systems, content and maintenance • - Elimination of centralized computers for storing information • E.g. Napster, each member contributes to pool of music files. • SETI@home faster than fastest supercomputer in world, • cost is 1% Jay Sheth Jay Sheth Jay Sheth

  16. Characteristics • Ad-hoc Connectivity • - Everything not connected to the internet • - Ad-hoc groups should be able to form ad-hoc networks to • collaborate • - Bluetooth and infrared have limited radius of accessibility • - P2P need to be designed to tolerate sudden disconnection/additions Jay Sheth Jay Sheth Jay Sheth

  17. Characteristics • Performance • - Significant concern • - Influenced by processing, storage, networking • - Aggregating distributed storage capacity e.g. Napster, Gnutella • - Aggregating computing cycles e.g.. SETI@Home • - Networking delays in WAN • - Bandwidth for large number of messages/files. Limits scalability of • system • - Optimize performance • Replication – Cope with disappearance of peers • Caching – Reduce path length • Intelligent routing – Minimize distance delay Jay Sheth Jay Sheth Jay Sheth

  18. Characteristics • Security • - For common distributed objects • - Multi-key encryption • - Sandboxing : External code doesn’t crash host • - Digital Rights Management to save intellectual property • Watermarking : Add a sign in file that is unrecognizable • - Reputation and accountability • Concept of good peer and freeloader Jay Sheth Jay Sheth Jay Sheth

  19. Characteristics • Transparency and Usability • - Naming transparency using URLs • - Administration transparency • - Network and device transparent i.e. work on internet, intranet and • private networks • User can use P2P applications in following manner • User of services, typically Web interfaces • Locally installed P2P software e.g.. Napster Jay Sheth Jay Sheth Jay Sheth

  20. Characteristics • Fault resilience • - Disconnection and node failures • - Special nodes called relays • - Store communication temporarily until destination reappears • - Magi : queue messages at source until presence of destination peer • detected • - Napster and Gnutella : Replication of crucial resources based on • file’s popularity • - Network failure can be solved by routing around the failure Jay Sheth Jay Sheth Jay Sheth

  21. Characteristics • Interoperability • - P2P systems • - Interoperate, communicate( what protocol), exchange data, same • level of security, QoS and reliability • - Still not supported Jay Sheth Jay Sheth Jay Sheth

  22. P2P Systems Jay Sheth Jay Sheth Jay Sheth

  23. Distributed Computing • - Processing scalability in massive multi-parameters systems • - Run by a central controller • - Fork and join mechanism • - Limitations • Independent small parts • Internet latencies • - Intel claim speed-ups from 15hours to 30 minutes in case of interest • rate swap modeling by using P2P Jay Sheth Jay Sheth Jay Sheth

  24. File Sharing • - Content storage and exchange is where P2P is most successful • Napster : • Search mechanism is centralized • File sharing mechanism is decentralized • Scalability limitations • Simplifies security mechanism Jay Sheth Jay Sheth Jay Sheth

  25. File Sharing • Kazaa : • Uses SuperNodes as local search hubs • Intelligent download system i.e. find and download from fastest connection. Failed transfers are automatically resumed Jay Sheth Jay Sheth Jay Sheth

  26. Collaboration • - Application level collaboration between users • - Event based applications such as Instant messaging, chat, online • games • - Challenges • Location of other peers (e.g.. NetMeeting requires to know other peers IP address) • Real time constraints • e.g.. Game DOOM Jay Sheth Jay Sheth Jay Sheth

  27. Platforms - Platforms have support for primary P2P components : naming, discovery, communication, security and resource aggregation - Candidates for future P2P platform : .net, JXTA Jay Sheth Jay Sheth Jay Sheth

  28. Comparison of Solutions Jay Sheth Jay Sheth Jay Sheth

  29. Future Work • P2P algorithms • World becomes decentralized, need for P2P algorithm to overcome • scalability, anonymity and connectivity problems • P2P applications • Most likely to succeed in future • P2P platforms • JXTA widely adopted Jay Sheth Jay Sheth Jay Sheth

  30. References • Peer-to-peer Computing • Dejan S. Milojicic, Vana Kalogeraki, Rajan Lukose, Kiran Nagaraja, • Jim Pruyne, Bruno Richard, Sami Rollins, Zhichen Xu • HP Laboratories Palo Alto • bsdq.org • http://www.bsdg.org/Jim/Peer2Peer/Paper/3214.html Jay Sheth

  31. Jay Sheth

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