1. Cmpe 494 Peer-to-Peer Computing Anıl Gürsel Didem Unat

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

3. 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

4. P2P Infrastructure Components

5. P2P Algorithms Central Index Algorithm Flooded Requests Algorithm Document Routing Algorithm

6. 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

7. 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@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

8. 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.

9. 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

10. 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

11. JXTA Virtual Network

12. Summary Decentralization Scalability Anonymity Self-Organization Cost of Ownership Performance Security Transparency and Usability