1. Peer-to-peer: an overview Selo TE 2005

2. P2P is not a new concept P2P is not a new technology P2P is not a new technology Oct. 29 1969: first transmission UCLA  Stanford Research Inst. (SRI) [UCSB, U. Of Utah]; Peer computing status among independent computing sites Oct. 29 1969: first transmission UCLA  Stanford Research Inst. (SRI) [UCSB, U. Of Utah]; Peer computing status among independent computing sites 1970s-1980s: ARPANET completed (1978); Usenet and DNS 1970s-1980s: ARPANET completed (1978); Usenet and DNS 1990s: NSFnet and Internet explosion 1990s: NSFnet and Internet explosion 1996: ICQ (bypassing DNS by offering own addressing scheme and allowing end points to be directly addressable with each other) 1996: ICQ (bypassing DNS by offering own addressing scheme and allowing end points to be directly addressable with each other)

3. Frameworks simplest form.. simplest form.. Models: Centralized Decentralized Controlled-decentralized | Hybrids Components: client, server, servents Main differences: how information is shared and how much information is shared

4. Centralized: Napster Napster used centralized servers to keep a catalog of available files. Napster used centralized servers to keep a catalog of available files. 1. User sends out request Napster searches central database Search request 2. The central server sends back a list of available files for download Search response Napster server user 3. Requesting user downloads the file directly from another Napster user computer Download from user

5. Centralized: pros and cons More effective, comprehensive searches More effective, comprehensive searches Access is controlled Access is controlled System has single points of entry; one fails could bring whole system down System has single points of entry; one fails could bring whole system down Broken links, out of date information. Broken links, out of date information.

6. Decentralized every user acts as a client, a server or both (servent). every user acts as a client, a server or both (servent). User connects to framework and becomes a member of the community, allowing others to connect through him/her User connects to framework and becomes a member of the community, allowing others to connect through him/her Users speak directly to other users with no intermediate or central authority Users speak directly to other users with no intermediate or central authority Not one entity controls the information that passes through the community Not one entity controls the information that passes through the community

7. Decentralized: Pros and Cons Peers speak directly with no central authority. Nobody owns the Gnutella Network and nobody can shut it down. Peers speak directly with no central authority. Nobody owns the Gnutella Network and nobody can shut it down. Isolated node failure can quickly and automatically be worked around. Isolated node failure can quickly and automatically be worked around. Free loading Free loading Scalability Scalability Searches are less effective and can be slow. Searches are less effective and can be slow. Gnutella network evolving to include “controlled decentralization” (limewire, bearshare, toadnode) Gnutella network evolving to include “controlled decentralization” (limewire, bearshare, toadnode)

8. Hybrids: controlled decentralization Characteristics of both centralized and decentralized frameworks Characteristics of both centralized and decentralized frameworks User’s computer may act as client, a server or a servent; there are server operators which may control which clients and/or servents are allowed to access a particular server. User’s computer may act as client, a server or a servent; there are server operators which may control which clients and/or servents are allowed to access a particular server. Examples: Morpheus, Groove Examples: Morpheus, Groove

9. Key application/function areas File sharing / Content Distribution File sharing / Content Distribution Not just mp3s/media sharing ones Not just mp3s/media sharing ones Distributed searching: Used to easily lookup and share files and offer content management (NextPage) Distributed searching: Used to easily lookup and share files and offer content management (NextPage) Instant Messaging Instant Messaging Jabber, IM Jabber, IM Distributed Computation: Distributed Computation: Use under utilized Internet and/or network resources for improving computation and data analysis Use under utilized Internet and/or network resources for improving computation and data analysis

10. Key application/function areas P2P groupware / Collaboration P2P groupware / Collaboration Cooperative publishing, messaging, group project management. Secure environments are offered in some products Cooperative publishing, messaging, group project management. Secure environments are offered in some products Development Frameworks; Development tools and suites Development Frameworks; Development tools and suites Project JXTA (Sun),.NET (Microsoft) Project JXTA (Sun),.NET (Microsoft) [See 2002 P2P Networking Overview - http://www.oreilly.com/catalog/p2presearch http://www.oreilly.com/catalog/p2presearch Also see: http://www.openp2p.com/pub/a/p2p/2000/12/05/book_ch01_meme.htmlhttp://www.openp2p.com/pub/a/p2p/2000/12/05/book_ch01_meme.html ] http://www.openp2p.com/pub/a/p2p/2000/12/05/book_ch01_meme.html

11. Classifying p2p… Another classification of p2p applications according to function and audience (Burton Group)