5. Server User User User User User User User User Search Request Search Response Download Centralized Model
6. P2P continued…… Decentralized System With a decentralized program each peer connect directly to other peers without being directed by a server. These connections are repeated making the resulting network, in theory, infinitely large. In reality this size of a network is constrained by the number of layers of computers a message has to travel through.
7. Search Request Search Relay Search Response Download User User User User User User User User User User Decentralized Model
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10. Napster continued…. Napster is a centralized or server-based P2P network. With a server-based network, there is a central list of information that is accessed by all the users of the system. Here is what happened when you decided to look for the song: 1.You opened the Napster utility. 2.Napster checked for an Internet connection. 3.If it found a connection, Napster logged you onto the central server. The main purpose of this central server was to keep an index of all the Napster users currently online and connect them to each other. It did not contain any of the MP3 files. 4.You typed in the title or artist of the song you were looking for. 5.The Napster utility on your computer queried the index server for other Napster computers online that had the song you requested.
11. Napster Continued…. 6.Whenever a match was found, the Napster server informed your computer where to find the requested file. 7.When the server replied, Napster built a list of these systems in the results window. 8.You clicked on the file(s) that interested you and then chose Download . 9.Your copy of Napster attempted to establish a connection with the system hosting the file you selected. 10.If a connection wa successfully made, the file began downloading. 11.Once the file wa downloaded, the host computer broke the connection with your system. 12.You opened up your MP3 player software and listened to the song.
33. Common Terms Used in P2P Peer A peer is anyone who is downloading or uploading the file Client The software that allows you to download and upload (share) files using Torrent. The Torrent client opens the .torrent file and allows connections from your peers. Tracker A tracker is a server that keeps track of which seeds and peers are in the swarm. Clients report information to the tracker periodically and in exchange receive information about other clients to which they can connect Seeder A seeder is a peer that has a complete copy of the torrent and still offers it for upload. The more seeders there are, the better the chances are for completion of the file. Leech A leech is usually a peer who has a negative effect on the swarm by having a very poor share ratio, however it can also refer to any peer without 100% of the data Swarm Together, all peers (including seeders) sharing a torrent are called a swarm.