Nowadays, many of us have a lot of media stored on our computers such as software, music, videos.

In the last few years users have started to share that content with each other across the net, whether legal or not.

This is something that has plagued the music industry
for several years. And now, mainly thanks to a system called
BitTorrent, the movie industry could face the same struggle.

But BitTorrent could also be the solution.

Hollywood is definitely interested in distributing its
movies over the net. King Kong is the first major film in the UK to be
released as a download at the same time as on DVD.

Users on the web will visit a download site and pull the
data onto their computers. Many users can be served at once but, if
demand is huge, users will effectively have to queue up and wait their
turn.

But there is another way to get hold of content and it
has caused a nightmare for the music industry of late, with users
sharing content amongst themselves, their peers.

Using a peer-to-peer (P2P) file-sharing program and a
decent internet connection, a user can make all his files available to
anyone else who is using the same program.

If you wanted to get hold of a particular song, your
file-sharing program would hunt for that file on other people’s hard
drives. When it finds it, it downloads a copy to your own computer.

The more users who download the file, the more places
there are for other users to get it. This reduces the likelihood of
bottlenecks, and is a very efficient way of distributing files across
the net.

Of course, it is illegal to share copyrighted material like that. But this has not stopped people doing it.

Larger files

More recent developments include being able to download different parts of the same file from different users.

But video files are much larger than music files and have slower upload times.

This is where BitTorrent comes in. It is an incredibly
efficient way of distributing large files, like video, across the net,
even when there is a high demand, and even when only one person has the
complete file.

The key is that a user’s computer does not need to wait until it has downloaded the entire file.

As soon as it has downloaded a chunk, it starts uploading it to any other users who do not yet have that chunk.

Similarly, your computer finds other users who have chunks that you are missing, and downloads many at once.

The group of machines sharing a file is called a swarm,
for obvious reasons. And the torrent of data flowing between them is
called a torrent. The more people in the swarm, the faster the file
spreads.

Using BitTorrent is not particularly difficult. There are many different BitTorrent programs freely available for download.

These manage the uploading and downloading for you,
maximising your internet connection, which can end up shifting
gigabytes in a session.

Once finished downloading, it is considered good manners
to stay online, allowing the program to continue sharing the file with
other users.

Broadband ‘hogs’

BitTorrent’s efficient use of broadband connections has
hugely increased the amount of traffic going across the net, because it
runs all users’ net connections flat out to deliver huge files.

Recent estimates say that around a third of all internet traffic is based around BitTorrent.

Some internet service providers think this is
unacceptable. Recently BT began clamping down on so-called "broadband
hogs", by starting to enforce a 40GB monthly limit.

Some ISPs go even further, breaking down customers’ net usage into
different types of activity, and discriminating against
bandwidth-hungry file-sharers.

So-called traffic-shaping is part of an ongoing battle between ISPs and BitTorrent programmers.

As network providers look for smarter ways to identify
torrent traffic, and reduce its impact on their network, more and more
help sites are springing up showing users how to encrypt their data to
avoid it being tracked and controlled.

Bulldog is one ISP which does not feel the need to
traffic shape its data flow. The company’s Gavin Young says this is
because there are different types of ISPs.

He told Click: "Some ISPs are what we call infrastructure-based, and that means they build their own networks.

"But other ISPs, maybe just for example a brand, are
paying money for the fibre, connectivity in that network, and maybe
they can’t even afford to buy a whole fibre and they’re just leasing
per megabit units of bandwidth. You’re going to be more inclined to try
to shape your traffic to keep your cost base down."

Jonathan Arber, a technology expert from Ovum, who
specialises in file-sharing, believes ISPs are right to be worried
about the amount of traffic that something like BitTorrent creates.

He said: "Certainly, you could see P2P as one of the
killer applications for broadband. What that means is that, if users
find that their broadband service is actually limiting the application
that they most want to use, they’ll simply go somewhere else."

By Spencer Kelly
news.bbc.co.uk