DOWNLOADING

Downloading Data in the Digital Age

Uploading and Downloading are related terms used to describe the transfer of electronic data between two computers or similar systems. More colloquially, they are sometimes applied to transfers to/from removable media such as CDs.

To download is to receive data from a remote or central system, such as a webserver, FTP server, mail server, or other similar systems. A download is any file that is offered for downloading or that has been downloaded.The word's primary usage comes in the form of a verb. Increasingly, websites that offer streaming media or media displayed in-browser, such as www.youtube.com, and which place restrictions on the ability of users to save these materials to their computers after they have been received, say that downloading is not permitted. That is, "download" is used to mean "receive and save" instead of simply "receive".

File Sharing

File sharing refers to the providing and receiving of digital files over a network, usually following the peer-to-peer (P2P) model, where the files are stored on and served by personal computers of the users. Most people who engage in file sharing on the Internet both provide (upload) files and receive files (download).

P2P file sharing is distinct from file trading in that downloading files from a P2P network does not require uploading, although some networks either provide incentives for uploading such as credits or force the sharing of files being currently downloaded.

Second P2P-Generation: Decentralization

After Napster encountered legal troubles, Justin Frankel of Nullsoft set out to create a network without a central index server, and Gnutella was the result. Unfortunately, the Gnutella model of all nodes being equal quickly died from bottlenecks as the network grew from incoming Napster refugees. FastTrack solved this problem by having some nodes be 'more equal than others'.

By electing some higher-capacity nodes to be indexing nodes, with lower capacity nodes branching off from them, FastTrack allowed for a network that could scale to a much larger size. Gnutella quickly adopted this model, and most current peer-to-peer networks implement this design, as it allows for large and efficient networks without central servers, Winmx also falls into this category.
Also included in the second generation are distributed hash tables (DHTs), which help solve the scalability problem by electing various nodes to index certain hashes (which are used to identify files), allowing for fast and efficient searching for any instances of a file on the network. This is not without drawbacks; perhaps most significantly, DHTs do not directly support keyword searching (as opposed to exact-match searching).

The best examples are Gnutella, Kazaa or eMule with Kademlia, whereby Kazaa has still a central server for logging in. eDonkey2000/Overnet, Gnutella, FastTrack and Ares Galaxy have summed up approx. 10.3 million users (as of April 2006, according to slyck.com). This number does not necessarily correspond to the actual number of persons who use these networks; it must be assumed that some use multiple clients for different networks.