A Bittorrent magnet link contains all the information needed to start
downloading the files from peers directly. It is a server-less way of
retrieving the right information to start downloading the requested
files. A magnet link therefor is theoretically all that is needed to
download files from other peers in the Bittorrent network. Magnet
links can be distributed by email, messaging and other forms of
communication but are most often found on the torrent sites that
usually offer both torrent and magnet links to their users.
A magnet consists of several parts:
- magnet: (This is the magnet link identifier)
- ?xt=urn:btih: (Defines a Bittorrent Info Hash, the Edonkey identifier would for instance look like this xt=urn:ed2k:)
- 5dee65101db281ac9c46344cd6b175cdcad53426 (The content hash)
- &dn=name (The name of the file)
The full magnet link would look like this:
Detailed information about additional Magnet Link parameters are
listed on Wikipedia. One useful parameter that has not been
mentioned yet is the
as= parameter which contains encrypted
information about a download source. This speeds up the process of
finding the first peers.
Main Advantages of Magnet Links
The main advantage for Bittorrent indexers is that they do not have to
store the torrents on their servers anymore which could be beneficial
for them in several ways. It could reduce the pressure from the media
creation industry and reduce hardware infrastructure expenses thanks
to less tracking and downloading.
The end users on the other hand benefit from Magnet Links as well. All
they need is the link to start downloading the files which makes them
independent from torrent indexers. It also allows them to distribute
the information more easily. Torrent indexers remain on the other hand
the main source of information for new files that are available for
Magnet Links use DHT
A tracker less environment should raise a question of identification.
How can a download be initiated ff there is no tracker to inform the
Bittorrent user about other users who download and seed the file? The
answer is DHT, Distributed hash tables. DHT is enabled by default in
popular clients such as uTorrent or Vuze. Without going into to much
detail, the hash of the magnet link is used to find peers using DHT.