Gnutella Network

Gnutella is a file sharing network. Gnutella actually is one of the most popular file sharign networks on the la red.
It is different from other exchange networks, like eDonkey2000. Gnutella is a pure P2P network. This is, all the nodes have the same function, weight and importance inside the network. The operation of the nerwork have three phases:

Entrance. In thi s phase a new node is connected to another that already is inside the network. How a node is found already connected is outside of the protocol, but normally the Gnutella clients are distributed with a list of nodes that expect they be alwyas connected.
A node can be connected to various nodes, and to rceeive connections of new nodes forming a random net structure.
Searches. When a node desires to seek a file, sends a message to all the nodes that are connected at the time. They seek locally if they offer it, and at the saem tiime they forward the search to all the nkdes that they are connected to. This strategy of diffusion is called flood of the network, and mechanisms ezist to avoid infinite cross-referneces and loops. When a petition arrives at a node that offers the fiel, is answered directly to the node that initiwted the search.
Download. The download is carried out directly from the nodeds that answered to the search of the flie. The files can be divided in various pieces served by different nodes, and the clients include a system of final verification of the integrity of the file. The flood produced by the phase of search is the most important weakness of this protocol. If there are many searches at the same time, the network flood full of messages of search thzt the nodes sent among them. Besides, this algorithm of search does not guarantee that the file be finally found even although some node of the network have it. Even so, the fact that it not uses a central server of search, as in the case of eDonkey2000, makes tis protocol stronger in case the nodes fail.
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Extraido de Limewire Blog