P2P with a Discovery, Lookup, and Content Server The server dominates as in a typical client/server architecture Peers are not permitted to connect with each other directly All resources are stored in the database of the server Major disadvantage of this model is that the server slows down if too many requests come up simultaneously There is single point of failure in server 哈工大计算机学院李全龙 Network Application Development P2P Application Development 16
哈工大计算机学院 李全龙 Network Application Development P2P Application Development 16 P2P with a Discovery, Lookup, and Content Server The server dominates as in a typical client/server architecture Peers are not permitted to connect with each other directly All resources are stored in the database of the server Major disadvantage of this model is that the server slows down if too many requests come up simultaneously There is single point of failure in server
Existing P2P Applications Napster Gnutella 哈工大计算机学院李全龙 Network Application Development P2P Application Development 17
哈工大计算机学院 李全龙 Network Application Development P2P Application Development 17 Existing P2P Applications Napster Gnutella
Centralized: Napster Napster used centralized servers to keep a catalog of available files. (3rd model) 1. User sends out Search reques↑ request Napster user Napster searches central database Search response server user 2. The central server sends back a list of available files for download Download from user user user t Requesting user downloads 3 he file directly from another Napster user computer 哈工大计算机学院李全龙 Network Application Development P2P Application Development 18
哈工大计算机学院 李全龙 Network Application Development P2P Application Development 18 Centralized: Napster Napster used centralized servers to keep a catalog of available files. (3rd model) 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 user user user 3. Requesting user downloads the file directly from another Napster user computer Download from user
Centralized: pros and cons pros More effective, comprehensive searches Access is controlled cons System has single points of entry: one fails could bring whole system down Broken links, out of date information 哈工大计算机学院李全龙 Network Application Development P2P Application Development 19
哈工大计算机学院 李全龙 Network Application Development P2P Application Development 19 Centralized: pros and cons pros More effective, comprehensive searches Access is controlled cons System has single points of entry; one fails could bring whole system down Broken links, out of date information
Decentralized Every user acts as a client, a server or both (servent) a User connects to framework and becomes a member of the community, allowing others to connect throug h him/her Users speak directly to other users with no intermediate or central authority Not one entity controls the information that passes through the community 哈工大计算机学院李全龙 Network Application Development P2P Application Development 20
哈工大计算机学院 李全龙 Network Application Development P2P Application Development 20 Decentralized 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 Users speak directly to other users with no intermediate or central authority Not one entity controls the information that passes through the community