How Peer to Peer (P2P) works

Peer to Peer (P2P) Technology – How It Works:

Ever wonder how P2P works? This guide will go over most of the major P2P services and how they work. Peer to Peer technology enables people to share files over a network on the Internet. Most people now use what is known as the second generation of P2P, which unlike its predecessors like Napter, the second generation does not have a centralized server, which makes it difficult to close.

How First Generation P2P Services Worked:

A connection is established when a peer finds another peer to connect to. Each pair exchanges an active pair and their addresses. When a connection has been established, the user can search for files. When a search is submitted, it connects to all nodes in its connection list. The results are then displayed and a connection is established.

How Second Generation P2P Services Worked:

Gnutella2: Hubs are used to find files quickly, eliminating the original “peer and find” method. Instead they store a list of files in all the “Sheets” (a couple) that are connected to it, which dramatically reduces search time.

Advantages: Unlike Napster, if a hub fails, your network remains up.

Disadvantages: It does not make the network more durable than the first generation of P2P.

Gnutella2: [http://www.gnutella.com]

FastTrack: Programs like Kazaa and iMesh use the FastTrack protocol. The normal pairs connect to a supernode that acts as a hub. Supernodes also connect to other supernodes, allowing search requests to move through the network very quickly. The peers then establish a direct connection with a client after a file has been found.

Advantages: Any client can become a supernode.

Disadvantages: File corruption occurs.

Clients include: Kazaa (www.kazaa.com), iMesh (www.imesh.com)

BitTorrent: .torrent files are used to store information about the file being shared. Once a torrent file is opened, the client connects to the crawler which tells the client where the file is located and what other pairs / seeders there are. BitTorrent works by transferring chunks of small files (even across multiple connections) while downloading. The files are checked for damage as the download continues. Leechers are people who download and don’t upload, and they are frowned upon on some sites, preventing them from downloading more.

Pros: Very fast for new and popular files.

Disadvantages: crawlers are unreliable and if it goes down, the file is lost.

Clients include: Azureus (www.azureus.com), Shareaza (www.shareaza.com).

EDonkey Network: Edonkey runs on the same principle as first-generation P2P, only anyone can become a server. Clients communicate with the server to download files, and random chunks can be downloaded in any order and then put together at the end.

Advantages: No file corruption, penalty for leeches.

Disadvantages: May unfairly penalize users.

Eonkey: [http://www.edonkey2000.com]

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