Magnet links are the direction Bittorrent seems to be heading.  Using Magnet links and utilizing DHT is definitely the way of the future.  But what are Magnet Links? And how do they work?  To understand this, we must first understand what DHT and PEX are, and how they work.

What is DHT / PEX?

DHT is a decentralized peer-to-peer network that most clients (uTorrent, Vuze, etc.) will join by default, even if they are currently not downloading any torrents.  Being on the DHT network will help you find peers and metadata when you are ready to begin downloading a torrent.

Seeing as this is a default network and it is mainly decentralized the need for trackers drastically decreases as they are vulnerable to being shut down for a number of reasons, or could suffer from denial of service.  As you can see from the image above:

[DHT], [Local Peer Discovery], and [Peer Exchange] all are able to track down Seeds / Peers on their own.

PEX (Peer Exchange) is another method of finding IP addresses.  It utilizes the knowledge of peers you are connected to, but obtaining a list of peers they are connected to.

Whereas the trackers below are able to do so as well, sometimes trackers go offline, so this method isn’t always reliable and we predict will become  less reliable in the future.  We predict more and more trackers are switching to this method of distribution, instead of hosting actual .torrent files, however this isn’t going to happen overnight.

Normally Torrent files are downloaded from downloaded from torrent sites, then a client like uTorrent or Vuze then calculates a hashurl (a kind of unique identifier) based on the files it is seeking to download.  It then retrieves the IP addresses of peers from a tracker (can be more than one) or uses DHT/PEX that have the same hashes and connects to those specific peers to download the desired content.

Sites such as The Pirate Bay can save on bandwith by calculating the hashes themselves allowing these Magnet Links to be downloaded instead of the actual .torrent files.  Using the torrent hash (included in the Magnet Link URL) clients immediately seek the addresses of peers on the DHT/PEX network and connect to them to download the .torrent file from them and then the desired content

Since the second method allows the .torrent file to be hosted by anyone, anywhere and can be accessed simply by feeding a link into a client, it is much more reliable.

Since the encrypted information in the .torrent file are still needed to initiate the downloading process, these files cannot be eliminated all-together, and must still be available by someone in the swarm.

Known Compatible Clients

uTorrent 1.8.5 (and higher)

Vuze 4.3.0.2 (and higher)

BitTorrent 6.3 (and higher)

BitComet 1.16 (and higher) [no magnet link support yet, only DHT/PEX]

Transmission 1.76 (and higher) [no magnet link support yet, only DHT/PEX]

Article Sources

thepiratebay.org (blog)

lifehacker.com

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