All about BitTorrent
You probably keep hearing about BitTorrent, but might not have any idea what it is. Or, perhaps you’ve downloaded a .torrent file, and have no idea how to open it. BitTorrent has been getting a lot more distribution, and it’s a good idea to understand what it’s all about.
BitTorrent is a method of distributing a file to a lot of people. It has nothing to do with Peer-to-Peer (P2P) technology like Limewire, Gnutella, Bearshare, or any of the others. This is because it’s not building a network. When you use BitTorrent, you aren’t sharing a folder. It’s all about distributing the effort of sharing the file among people who are interested in it.
Let’s say a person has a 50 MB video they want to share with the public. If they have 1,000 people who want to download it, and they just host it on a web site somewhere, then this person has to support 50 MB x 1,000 downloads, or 50,000 MB (around 49 GB) of download bandwidth. That’s a lot by most standards.
Now, let’s imagine a different scenario. Let’s say that the person cuts the video into four parts, and starts uploading it to four different people. So, person A gets the first quarter, person B gets the second, C gets the third, and D gets the fourth. The original hoster has only uploaded the video one time, yet uploaded the parts to four other people. Person A, B, C, and D do not yet have complete files, they only have a fourth. However, now imagine that persons A, B, C, and D can now upload to each other. A can download the remaining parts from B, C, and D; B can download from A, C, and D, and so on. Basically, splitting things up this way mean that the other people who downloaded parts can upload the parts they downloaded to other people. Eventually, A, B, C, and D can all get the file, with the original person only having uploaded the file once.
Now, let’s add person E, another person interested in the file. Person E can download parts from the original poster, but can also download parts from A, B, C, and D. Even if the original poster doesn’t upload anymore, the file can be obtained by downloading from A, B, C, and D. The entire bandwidth of the upload can be distributed across the people who are downloading. If everyone except the original poster remains connected until E downloads the file, then the file will have been distributed five times (to A, B, C, D, and E), for an upload amount of 5 x 50 MB. However, the original poster only uploaded the file once for 50 MB. If the original poster had just hosted the file, they would have uploaded 250 MB.
This is a simplification of what happens, but is accurate enough to explain how it distributes the bandwidth cost. The truth is, the file will get cut into a lot smaller pieces, and there will probably be a lot more people involved. The more people involved, the greater the ability to download. If the original hoster didn’t have much bandwidth, that would throttle the amount that people could download at a time. Let’s say that the original hoster had the ability to upload at a rate of 50 KB/s. If one person was downloading, then they could get the file in 1,024 seconds. However, if two people were downloading, it would take 2,048 seconds. Imagine that there were a fifty people downloading the file at once — it would take everybody over fourteen hours to download.
With BitTorrent, that limit isn’t there, because everyone shares in the upload. The more people involved, the better off the bandwidth. That’s what makes BitTorrent so powerful: rather than causing downloads to get slower as more people get involved, it gets faster. I have one torrent downloading right now that is getting speeds around 540 KB/s. Not all torrents get that, but it’s even rarer to get web servers with that sort of download available, especially with a popular file.
This adds an interesting kharmic element to this mix. If everyone downloaded a file, then immediately quit uploading, then this doesn’t work. That’s why there’s a golden rule of BitTorrent: stay connected until you’ve uploaded as much as you’ve downloaded. This is referred to as a ratio — the ratio of what you’ve uploaded to what you’ve downloaded. You should stay connected until this is equal to or greater than 1.
Additionally, it also means that the power of the torrent will scale depending on the popularity. If no one wants a file, then the torrent will never pick up steam. A file’s popularity is directly correlates to the power of its torrent.
Those are the basics to understanding what BitTorrent does. These steps involve creating a .torrent file, with information about the file to distribute; this file gets uploaded to a tracker (a server that works to announce to everyone who’s connected to the torrent); then the .torrent file is uploaded somewhere for people to download. From a user’s perspective, all that’s needed is to download the .torrent file, open it in a BitTorrent client, let the download complete, then wait for the upload to download ratio to reach 1. It’s important to note, however, that some trackers strictly enforce that ratio — don’t hit it, and get banned from that tracker.
BitTorrent has been getting a bad rap because of its use in illegal trading, including music, videos, DVDs, software, and more. This is important to know, because of the way BitTorrent works: if you download things with BitTorrent, you are also uploading at the same time. If, say, the RIAA or MPAA note that you’ve been uploading copyrighted material, you’re running the risk of getting sued. Yes, it’s happened.
If you don’t have one yet, you probably should go ahead and download a BitTorrent client. The official BitTorrent client is actually decent, though there are many third party options available as well. As BitTorrent is getting more mainstream, it’s a good idea to install it, because you’ll eventually come across .torrent files.
