Torrents are different from FTP. With FTP, you download a file or files from a single source. Torrents work by downloading from as many sources available.
Anatomy Of A Torrent File -
A file or files are indexed into pieces. Each piece is numbered from 1 to n; n being the number of the last piece.
Each piece is also given a hash value using SHA-1 hashing. Without getting technical, all this does is enable the
torrent program to verify the integrity of the data your receive. File names and directory structures are also stored
in a torrent file. Last, but not least, the URL address of the torrent tracker.
The Participants In A Torrent -
The main participant in a torrent is the torrent tracker. It is a server which handles the list of peers connected
to a torrent. Peers are divided into two groups, seeders and leechers. Seeders are those who have the complete file
or files associated with a torrent. Leechers are everyone else trying to get that file or files.
How It Works -
When you start a torrent session, your computer connects with a torrent tracker. The torrent tracker keeps track of
everyone seeding and leeching a particular torrent. Upon connecting to a tracker, you receive a list of peers
associated with a particular torrent. This list of peers will consist of the IP addresses of seeders and leechers.
This group of seeders and leechers are a called a swarm. Your torrent program makes a request to all the peers in
your swarm for information on what pieces they have. Upon receiving a list from each peer, your torrent program will
make a request for a piece. The torrent program of the peer you make a request to will make the determination of
whether or not to send that piece to you. Take note of this because you will be connected to several peers but will
probably only download from a few. Upon completion of a piece, your torrent program sends out a small message to all
the peers in your swarm that you have completed a piece, at which point in time your peers may request that piece from
you. Over time, you will eventually receive the complete file or files.
Download speeds vary based on your maximum download speed and, more importantly, the maximum upload speeds of your
peers. You will occassionally run across peers who have some serious bandwidth. You'll find yourself
downloading files at some insane speeds. Other times, you'll be connected to peers who have small upload
capabilities and it can take days to download a torrent. The trick is to forget about the torrent until it finishes.
Torrent Sites -
There are two different types of torrent sites, ratio and non-ratio.
Ratio sites typically require you to register with the site. This is so they can keep track of how much you share
versus how much you download. These types of sites require you to maintain a 1.0 ratio or higher to stay in good
graces. The advantages of these types of sites is that they usually have a lot of seeders with large bandwidth,
upwards of 2-20 megabits; that's approximately 250kB-2.5MBs of bandwidth. It's really nice for files that
have become recently available.
Non-ratio sites typically do not require you to register with their site. The advantages of these sites is that you
do not have to share the torrent you download to a 1.0 ratio. The disadvantages is that there is no incentive for
others to do the same either so ocassionally you will run across torrents with no seeders. That means you will not
be able to complete that download. Downloads also tend to be slower.
There's nothing wrong with using either types of sites. Once you become more familiar with torrents and torrent
sites, you'll find certain sites that you like and use quite a bit.
If you really want to get technical about the torrent specification, go to this site. It has EVERYTHING you need to
know abou what goes on with a torrent.