Courtesy BitTorrent, Inc.

BitTorrent is a protocol that enables fast downloading of large files using minimum Internet bandwidth. It costs nothing to use and includes no spyware or pop-up advertising.
Unlike other download methods, BitTorrent maximizes transfer speed by gathering pieces of the file you want and downloading these pieces simultaneously from people who already have them. This process makes popular and very large files, such as videos and television programs, download much faster than is possible with other protocols.
In this article, we'll examine how BitTorrent works and how it is different from other file-distribution methods. In addition, you'll learn how to use BitTorrent and what the future might hold for this innovative approach to serving files over the Internet.

BitTorrent Speak Like most Internet phenomena, BitTorrent has its own jargon. Some of the more common terms related to BitTorrent include: Leeches - People who download files but do not share files on their own computer with others Seed or seeder - A computer with a complete copy of a BitTorrent file (At least one seed computer is necessary for a BitTorrent download to operate.) Swarm - A group of computers simultaneously sending (uploading) or receiving (downloading) the same file .torrent - A pointer file that directs your computer to the file you want to download Tracker - A server that manages the BitTorrent file-transfer process

Traditional Client-Server Downloading
To understand how BitTorrent works and why it is different from other file-serving methods, let's examine what happens when you download a file from a Web site. It works something like this:

• You open a Web page and click a link to download a file to your computer.
• The Web browser software on your computer (the client) tells the server (a central computer that holds the Web page and the file you want to download) to transfer a copy of the file to your computer.
• The transfer is handled by a protocol (a set of rules), such as FTP (File Transfer Protocol) or HTTP (HyperText Transfer Protocol).

Client-server download process

The transfer speed is affected by a number of variables, including the type of protocol, the amount of traffic on the server and the number of other computers that are downloading the file. If the file is both large and popular, the demands on the server are great, and the download will be slow.
For more information about Web servers and the traditional client-server download, see How Web Servers Work.
Next, we'll look at how peer-to-peer sharing differs from this process.

Peer-to-peer file sharing is different from traditional file downloading. In peer-to-peer sharing, you use a software program (rather than your Web browser) to locate computers that have the file you want. Because these are ordinary computers like yours, as opposed to servers, they are called peers. The process works like this:

• You run peer-to-peer file-sharing software (for example, a Gnutella program) on your computer and send out a request for the file you want to download.
• To locate the file, the software queries other computers that are connected to the Internet and running the file-sharing software.
• When the software finds a computer that has the file you want on its hard drive, the download begins.
• Others using the file-sharing software can obtain files they want from your computer's hard drive.

Gnutella's peer-to-peer download process

The file-transfer load is distributed between the computers exchanging files, but file searches and transfers from your computer to others can cause bottlenecks. Some people download files and immediately disconnect without allowing others to obtain files from their system, which is called leeching. This limits the number of computers the software can search for the requested file.
For more information about file sharing and the peer-to-peer download, see How Gnutella Works and How Kazaa Works.


Unlike some other peer-to-peer downloading methods, BitTorrent is a protocol that offloads some of the file tracking work to a central server (called a tracker). Another difference is that it uses a principal called tit-for-tat. This means that in order to receive files, you have to give them. This solves the problem of leeching -- one of developer Bram Cohen's primary goals. With BitTorrent, the more files you share with others, the faster your downloads are. Finally, to make better use of available Internet bandwidth (the pipeline for data transmission), BitTorrent downloads different pieces of the file you want simultaneously from multiple computers. Here's how it works:

BitTorrent's peer-to-peer download process

• You open a Web page and click on a link for the file you want.
• BitTorrent client software communicates with a tracker to find other computers running BitTorrent that have the complete file (seed computers) and those with a portion of the file (peers that are usually in the process of downloading the file).
• The tracker identifies the swarm, which is the connected computers that have all of or a portion of the file and are in the process of sending or receiving it.
• The tracker helps the client software trade pieces of the file you want with other computers in the swarm. Your computer receives multiple pieces of the file simultaneously.
• If you continue to run the BitTorrent client software after your download is complete, others can receive .torrent files from your computer; your future download rates improve because you are ranked higher in the "tit-for-tat" system.

Downloading pieces of the file at the same time helps solve a common problem with other peer-to-peer download methods: Peers upload at a much slower rate than they download. By downloading multiple pieces at the same time, the overall speed is greatly improved. The more computers involved in the swarm, the faster the file transfer occurs because there are more sources of each piece of the file. For this reason, BitTorrent is especially useful for large, popular files.


To use BitTorrent for file downloads, you need to install the BitTorrent client software. You may also need to tweak your firewall and network router (if you use these) to accept BitTorrent files. We'll give you all the details to get started. But first, here's a synopsis of the steps:

1. Download and install the BitTorrent client software.
2. Check and configure firewall and/or router for BitTorrent (if applicable).
3. Find files to download.
4. Download and open the .torrent pointer file.
5. Let BitTorrent give and receive pieces of the file.
6. Stay connected after the download completes to share your .torrent files with others.

Distributing with BitTorrent If you have a large file you want to serve, BitTorrent can help you make the best use of your available bandwidth. To make a file available as a .torrent file, you need access to a tracker and to a Web server. In addition, you'll need to download and install the software that creates the .torrent file from www.bittorrent.com. You can find detailed instructions for distributing files with BitTorrent on the official BitTorrent Web site.

Download the BitTorrent Client Software
BitTorrent is open-source software, which means the program is available to you and to software developers for free (see What does "open source" mean?). Therefore, some developers have created their own versions of BitTorrent software, and you can choose from a number of client programs. (Note: This article assumes you are using the official version. If you want to experiment with different clients, see Brian's BitTorrent FAQ and Guide for a list.)
To start off, go to BitTorrent.com and click the link for the client software that matches your operating system. After you download the client software, double-click on the desktop icon to install it. The installation program is quick, and it displays this window when it is complete:

You'll also see Bram Cohen's Web page, where you can send donations to support development of BitTorrent. Mr. Cohen develops and distributes BitTorrent as open-source software at no cost to users or other developers.
Check and Configure Firewall

Is It Legal? BitTorrent is perfectly legal to use. However, it is illegal to download copyrighted materials in most countries. So if the file you're downloading is copyrighted, then what you're doing is not legal. See the "Legal Ramifications" section to learn more.

If you have a firewall installed on your computer, you will obtain faster download rates if you configure it to have an open pathway for BitTorrent file transfers. A firewall protects your system from intruders by disallowing unauthorized access to your computer's ports. A port is a way for Internet communications to travel into and out of your computer. Ports are numbered, and each communication type has a standard port number. See How Web Servers Work to learn more. BitTorrent also uses specific port numbers, normally ports 6881 through 6889. Because firewalls block these ports by default, you'll need to configure your firewall to accept this incoming traffic in order to receive .torrent files. You may also have to enable port forwarding of your computer's IP address for ports 6881 through 6889 so that other BitTorrent computers can find you. Because every product is unique, check the documentation or product Web site for your firewall/router for specific instructions on how to accomplish these tasks. You can also check out PortForward.com for help.
Once you have everything set up, you'll probably want to find some files to download. Next, we'll discuss where to look and the legal ramifications of downloading what you find.

After you set up your computer, you're ready to download .torrent files. You can search for the term ".torrent" using an Internet search engine to find sites that offer BitTorrent files. There are also a number of sites dedicated to BitTorrent file searching. These include isoHunt and TorrentSpy. Other sites that offer BitTorrent files directly include bt.etree.org for shareable music, Legal Torrents for music, videos and books, and BT on EFnet for recent television shows. When you find the file you want, right-click the .torrent link, choose "save target as" and save the file in a convenient place on your computer, such as the Windows desktop. The .torrent file, which is a pointer to the actual file you want, will download quickly. Next, double-click the .torrent file you saved to your computer. The BitTorrent client software displays and starts the download process:

As we mentioned before, the more computers in the sending/receiving swarm, the quicker the download process. If you are downloading a file with only a few other computers in the swarm, the transfer speed will be relatively slow.
After the download is complete, leave the BitTorrent client software open so that other peers can download .torrent files from your computer.*

Peers using BitTorrent can download only .torrent files from your computer. Once you have a complete copy of a file, your computer becomes a potential seed for that file -- as long as you're still running the software. Sharing what you have causes speedier BitTorrent downloads for you in the future. You can leave the client software running for a few hours or overnight.* Simply close the software when you're done.

Expensive Uploads? Does your ISP charge for uploads? It's rare, but it's possible. Before leaving the BitTorrent client software open overnight, be sure your ISP doesn't charge for uploads -- otherwise, moving up in the tit-for-tat hierarchy could end up costing you an arm and a leg.

Legal Ramifications Similar to other peer-to-peer software, BitTorrent can be used to download copyrighted material. Because BitTorrent handles large files remarkably well, it is especially popular for downloading video files. The Motion Picture Association of America has filed countless lawsuits, causing at least many high-traffic .torrent download sites to shut down.
BitTorrent itself is perfectly legal to use. When you select a file to download, however, it is your responsibility to make sure the file not copyrighted. BitTorrent downloads are not anonymous; information about your computer's IP address and the files you download can be traced back to you.
Despite its improper use by distributors of copyrighted material, the BitTorrent program itself both legal and innovative. With additions such as tit-for-tat and an open-source philosophy, BitTorrent will likely build a legacy of its own while serving as a bridge to the next generation of file-serving software.

If you download many programs and files off the Internet, you've probably encountered ZIP files before. This compression system is a very handy invention, especially for Web users, because it lets you reduce the overall number of bits and bytes in a file so it can be transmitted faster over slower Internet connections, or take up less space on a disk. Once you download the file, your computer uses a program such as WinZip or Stuffit to expand the file back to its original size. If everything works correctly, the expanded file is identical to the original file before it was compressed. At first glance, this seems very mysterious. How can you reduce the number of bits and bytes and then add those exact bits and bytes back later? As it turns out, the basic idea behind the process is fairly straightforward. In this article, we'll examine this simple method as we take a very small file through the basic process of compression.

Most types of computer files are fairly redundant -- they have the same information listed over and over again. File-compression programs simply get rid of the redundancy. Instead of listing a piece of information over and over again, a file-compression program lists that information once and then refers back to it whenever it appears in the original program.
As an example, let's look at a type of information we're all familiar with: words.
In John F. Kennedy's 1961 inaugural address, he delivered this famous line:

"Ask not what your country can do for you -- ask what you can do for your country." The quote has 17 words, made up of 61 letters, 16 spaces, one dash and one period. If each letter, space or punctuation mark takes up one unit of memory, we get a total file size of 79 units. To get the file size down, we need to look for redundancies.
Immediately, we notice that:

• "ask" appears two times
• "what" appears two times
• "your" appears two times
• "country" appears two times
• "can" appears two times
• "do" appears two times
• "for" appears two times
• "you" appears two times

Ignoring the difference between capital and lower-case letters, roughly half of the phrase is redundant. Nine words -- ask, not, what, your, country, can, do, for, you -- give us almost everything we need for the entire quote. To construct the second half of the phrase, we just point to the words in the first half and fill in the spaces and punctuation.
We'll look at how file-compression systems deal with redundancy in more detail in the next section.

Most compression programs use a variation of the LZ adaptive dictionary-based algorithm to shrink files. "LZ" refers to Lempel and Ziv, the algorithm's creators, and "dictionary" refers to the method of cataloging pieces of data. The system for arranging dictionaries varies, but it could be as simple as a numbered list. When we go through Kennedy's famous words, we pick out the words that are repeated and put them into the numbered index. Then, we simply write the number instead of writing out the whole word.
So, if this is our dictionary:

ask what your country can do for you

Our sentence now reads:

"1 not 2 3 4 5 6 7 8 -- 1 2 8 5 6 7 3 4"

If you knew the system, you could easily reconstruct the original phrase using only this dictionary and number pattern. This is what the expansion program on your computer does when it expands a downloaded file. You might also have encountered compressed files that open themselves up. To create this sort of file, the programmer includes a simple expansion program with the compressed file. It automatically reconstructs the original file once it's downloaded.
But how much space have we actually saved with this system? "1 not 2 3 4 5 6 7 8 -- 1 2 8 5 6 7 3 4" is certainly shorter than "Ask not what your country can do for you; ask what you can do for your country;" but keep in mind that we need to save the dictionary itself along with the file.
In an actual compression scheme, figuring out the various file requirements would be fairly complicated; but for our purposes, let's go back to the idea that every character and every space takes up one unit of memory. We already saw that the full phrase takes up 79 units. Our compressed sentence (including spaces) takes up 37 units, and the dictionary (words and numbers) also takes up 37 units. This gives us a file size of 74, so we haven't reduced the file size by very much.
But this is only one sentence! You can imagine that if the compression program worked through the rest of Kennedy's speech, it would find these words and others repeated many more times. And, as we'll see in the next section, it would also be rewriting the dictionary to get the most efficient organization possible.


In our previous example, we picked out all the repeated words and put those in a dictionary. To us, this is the most obvious way to write a dictionary. But a compression program sees it quite differently: It doesn't have any concept of separate words -- it only looks for patterns. And in order to reduce the file size as much as possible, it carefully selects which patterns to include in the dictionary. If we approach the phrase from this perspective, we end up with a completely different dictionary.
If the compression program scanned Kennedy's phrase, the first redundancy it would come across would be only a couple of letters long. In "ask not what your," there is a repeated pattern of the letter "t" followed by a space -- in "not" and "what." If the compression program wrote this to the dictionary, it could write a "1" every time a "t" were followed by a space. But in this short phrase, this pattern doesn't occur enough to make it a worthwhile entry, so the program would eventually overwrite it.
The next thing the program might notice is "ou," which appears in both "your" and "country." If this were a longer document, writing this pattern to the dictionary could save a lot of space -- "ou" is a fairly common combination in the English language. But as the compression program worked through this sentence, it would quickly discover a better choice for a dictionary entry: Not only is "ou" repeated, but the entire words "your" and "country" are both repeated, and they are actually repeated together, as the phrase "your country." In this case, the program would overwrite the dictionary entry for "ou" with the entry for "your country."
The phrase "can do for" is also repeated, one time followed by "your" and one time followed by "you," giving us a repeated pattern of "can do for you." This lets us write 15 characters (including spaces) with one number value, while "your country" only lets us write 13 characters (with spaces) with one number value, so the program would overwrite the "your country" entry as just "r country," and then write a separate entry for "can do for you." The program proceeds in this way, picking up all repeated bits of information and then calculating which patterns it should write to the dictionary. This ability to rewrite the dictionary is the "adaptive" part of LZ adaptive dictionary-based algorithm. The way a program actually does this is fairly complicated, as you can see by the discussions on Data-Compression.com.
No matter what specific method you use, this in-depth searching system lets you compress the file much more efficiently than you could by just picking out words. Using the patterns we picked out above, and adding "__" for spaces, we come up with this larger dictionary:

ask__ what__ you r__country __can__do__for__you

And this smaller sentence:

"1not__2345__--__12354"

The sentence now takes up 18 units of memory, and our dictionary takes up 41 units. So we've compressed the total file size from 79 units to 59 units! This is just one way of compressing the phrase, and not necessarily the most efficient one. (See if you can find a better way!)
So how good is this system? The file-reduction ratio depends on a number of factors, including file type, file size and compression scheme.
In most languages of the world, certain letters and words often appear together in the same pattern. Because of this high rate of redundancy, text files compress very well. A reduction of 50 percent or more is typical for a good-sized text file. Most programming languages are also very redundant because they use a relatively small collection of commands, which frequently go together in a set pattern. Files that include a lot of unique information, such as graphics or MP3 files, cannot be compressed much with this system because they don't repeat many patterns (more on this in the next section).
If a file has a lot of repeated patterns, the rate of reduction typically increases with file size. You can see this just by looking at our example -- if we had more of Kennedy's speech, we would be able to refer to the patterns in our dictionary more often, and so get more out of each entry's file space. Also, more pervasive patterns might emerge in the longer work, allowing us to create a more efficient dictionary.
This efficiency also depends on the specific algorithm used by the compression program. Some programs are particularly suited to picking up patterns in certain types of files, and so may compress them more succinctly. Others have dictionaries within dictionaries, which might compress efficiently for larger files but not for smaller ones. While all compression programs of this sort work with the same basic idea, there is actually a good deal of variation in the manner of execution. Programmers are always trying to build a better system.

The type of compression we've been discussing here is called lossless compression, because it lets you recreate the original file exactly. All lossless compression is based on the idea of breaking a file into a "smaller" form for transmission or storage and then putting it back together on the other end so it can be used again. Lossy compression works very differently. These programs simply eliminate "unnecessary" bits of information, tailoring the file so that it is smaller. This type of compression is used a lot for reducing the file size of bitmap pictures, which tend to be fairly bulky. To see how this works, let's consider how your computer might compress a scanned photograph.
A lossless compression program can't do much with this type of file. While large parts of the picture may look the same -- the whole sky is blue, for example -- most of the individual pixels are a little bit different. To make this picture smaller without compromising the resolution, you have to change the color value for certain pixels. If the picture had a lot of blue sky, the program would pick one color of blue that could be used for every pixel. Then, the program rewrites the file so that the value for every sky pixel refers back to this information. If the compression scheme works well, you won't notice the change, but the file size will be significantly reduced.
Of course, with lossy compression, you can't get the original file back after it has been compressed. You're stuck with the compression program's reinterpretation of the original. For this reason, you can't use this sort of compression for anything that needs to be reproduced exactly, including software applications, databases and presidential inauguration speeches.

The MP3 movement is one of the most amazing phenomena that the music industry has ever seen. Unlike other movements -- for example, the introduction of the cassette tape or the CD -- the MP3 movement started not with the industry itself but with a huge audience of music lovers on the Internet. The MP3 format for digital music has had, and will continue to have, a huge impact on how people collect, listen to and distribute music.


Not everyone is happy with the rise in popularity of the MP3 format. Some audio enthusiasts say that most MP3 files can't compare to a CD or vinyl album version of the same song. Others go so far as to claim that the way sound engineers mix music is changing because of MP3s, and not necessarily in a good way.
­If you have ever wondered how MP3 files work, or if you have heard about MP3 files and wondered how to use them yourself, then this article is for you! In this article, you will learn about the MP3 file format and how you can start downloading, listening to and saving MP3 files onto CDs!

Search for ­MP3 Files at Alibaba - the world’s largest online base of suppliers and importers.

Related Products:

• MP3 Adapter
• MP3 Amplifier
• MP3 Bag

• MP3 Batteries
• MP3 Bluetooth Headset
• MP3 Cable­

­
If you've read How CDs Work, then you know something about how CDs store music. A CD stores a song as digital information. The data on a CD uses an uncompressed, high-resolution format. Here's what happens when a CD is created:

• Music is sampled 44,100 times per second. The samples are 2 bytes (16 bits) long.
• Separate samples are taken for the left and right speakers in a stereo system.

So a CD stores a huge number of bits for each second of music:

44,100 samples/second * 16 bits/sample * 2 channels = 1,411,200 bits per second

Let's break that down: 1.4 million bits per second equals 176,000 bytes per second. If an average song is three minutes long, then the average song on a CD consumes about 32 million bytes (or 32 megabytes) of space. Even with a high-speed cable or DSL modem, it can take several minutes to download just one song. Over a 56K dial-up modem, it would take close to two hours.
The MP3 format is a compression system for music. The goal of using MP3 is to compress a CD-quality song by a factor of 10 to 14 without noticeably affecting the CD-quality sound. With MP3, a 32-megabyte song on a CD compresses down to about 3 MB. This lets you download a song much more quickly, and store hundreds of songs on your computer's hard disk.


Is it possible to compress a song without hurting its quality? We use compression algorithms for images all the time. For example, a .gif file is a compressed image. So is a .jpg file. We create .zip files to compress text. So we're familiar with compression algorithms for images and words and we know they work. To make a good compression algorithm for sound, a technique called perceptual noise shaping is used. It's "perceptual" partly because the MP3 format uses characteristics of the human ear to design the compression algorithm. For example:

• There are certain sounds that the human ear cannot hear.
• There are certain sounds that the human ear hears much better than others.
• If there are two sounds playing simultaneously, we hear the louder one but cannot hear the softer one.

Using facts like these, certain parts of a song can be eliminated without significantly hurting the quality of the song for the listener. Compressing the rest of the song with well-known compression techniques shrinks the song considerably -- by a factor of 10 at least. When you're done creating an MP3 file, what you have is a "near-CD-quality" song. The MP3 version of the song does not sound exactly the same as the original CD song because some of it has been removed.
Not all MP3 files are equal. Let's take a look at the different ends of the MP3 spectrum in the next section.
The MP3 compression format creates files that don't sound exactly like the original recording -- it's a lossy format. In order to decrease the size of the file significantly, MP3 encoders have to lose audio information. Lossless compression formats don't sacrifice any audio information. But that also means that lossless compression files are larger than their lossy counterparts.

You can choose how much information an MP3 file will retain or lose during the encoding and compression process. It's possible to create two different MP3 files with different sound quality and file sizes from the same source of data. The key is the bit rate -- the number of bits per second encoded in the MP3 file.

Most MP3 encoding software allows the user to select the bit rate when converting files into the MP3 format. The lower the bit rate, the more information the encoder will discard when compressing the file. Bit rates range from 96 to 320 kilobytes per second (Kbps). Using a bit rate of 128 Kbps usually results in a sound quality equivalent to what you'd hear on the radio. Many music sites and blogs urge people to use a bit rate of 160 Kbps or higher if they want the MP3 file to have the same sound quality as a CD.

Some audiophiles -- people who seek out the best ways to experience music -- look down on the MP3 format. They argue that even at the highest bit rate settings, MP3 files are inferior to CDs and vinyl records. But other people argue that it's impossible for the human ear to detect the difference between an uncompressed CD file and an MP3 encoded with a 320 Kbps bit rate.

There's no denying that, quality issues aside, the MP3 format is changing music. With music services like Amazon and eMusic, customers can buy music by the song. In a way, the music industry is returning to its roots -- the music single is becoming popular after nearly dying out during the CD era.

In addition, some musicians and audio engineers say that the MP3 format is changing the way music studios mix recordings. They say that the MP3 format "flattens" out the dynamics -- the differences in pitch and volume -- in a song. As a result, much of the new music coming out of the industry has a similar sound, and there's not as much of a focus on creating a dynamic listening experience. Why work that hard on creating a complex sound if no one can detect it [source: Levine]?
From this description, you can see that MP3 is nothing magical. It's simply a file format that compresses a song into a smaller size so it is easier to move around and store on your home computer -- or your portable music player.
Knowing about the MP3 format isn't half as interesting as using it. The MP3 movement -- consisting of the MP3 format and the Web's ability to advertise and distribute MP3 files -- has done several things for music:

• It has made it easy for anyone to distribute music at nearly no cost (or for free).
• It has made it easy for anyone to find music and access it instantly.
• It has taught people a great deal about manipulating sound on a computer.

Technology has made it easier to download and play your favorite music.

That third one was accidental but important. A big part of the MP3 movement is the fact that it has brought an incredible array of powerful tools to desktop computers and given people a reason to learn how they work. Because of these tools, it is now extremely easy for you to:

• Download an MP3 file from a Web site and play it
• Rip a song from a music CD and play it directly or encode it as an MP3 file
• Record a song yourself, convert it to an MP3 file and make it available to the world
• Convert MP3 files into CD files and create your own audio CDs from MP3 files on the Web
• Rip songs off of various music CDs and recombine them into your own custom CDs
• Store hundreds of MP3 files on data CDs
• Load MP3 files into tiny portable players and listen to them wherever you go

Let's look at of the many different things you can do with MP3 files and the software that makes it possible.

If you would like to download and listen to MP3 files on your computer, then you need:

• A computer
• A sound card and speakers for the computer (If your computer has speakers, it has a sound card.)
• An Internet connection (If you are browsing the Web to read this article, then you have an Internet connection and it is working fine.)
• An MP3 player (a software application you can download from the Web in 10 minutes)

If you have recently purchased a new computer, chances are it already has software that can play MP3 files installed on its hard disk. The easiest way to find out if you already have an MP3 player installed is to download an MP3 file and try to double-click on it. If it plays, you're set. If not, you need to download a player, which is very easy to do.
There are literally thousands of sites on the Web where you can download MP3 files. Go to one of these sites, find a song and download it to your hard disk. Most MP3 sites let you either listen to the song as a streaming file or download it -- you'll probably want to download it, if you want to save a copy for later. Most songs range between 2 and 4 MB, so it will take 10 to 15 minutes unless you have a high-speed Internet connection. Once the song has finished downloading, try to double-click on the file and see what happens. If your computer plays it, then you're set.


If you find that you cannot play it, then you need to download an MP3 player. There are dozens of players available, and most of them are free or shareware -- shareware is extremely inexpensive.
You're now ready to begin collecting MP3 files and saving them on your computer. Many people have hundreds of songs they have collected, and they create jukebox-like playlists so that their computer can play them all day long!
Many people who start collecting MP3 files find that they want to listen to them in all kinds of places. Small, portable MP3 players answer this need. These players are like portable cassette players except that they are smaller.
These players plug into your computer's FireWire or USB port to transfer the data. A software application lets you transfer your MP3s into the player by simply dragging the files. See How MP3 Players Work for details.

If you have a CD collection and would like to convert songs from your CDs into MP3 files, you can use ripper and encoder software to do just that. A ripper copies the song's file from the CD onto your hard disk. The encoder compresses the song into the MP3 format. By encoding songs, you can play them on your computer or take them with you on your MP3 player.
If you have a writable CD drive in your computer, there are two ways to save your MP3 files on a CD:

• You can write the MP3 files themselves onto a data CD in order to save them and clear some space on your hard disk. You can then listen to the files on any computer. Some car stereos and DVD players let you play data-encoded MP3s, too. Because the file size is much smaller than a CD file, you can fit many more songs onto a CD when you use the MP3 file format.
• You can convert (decode) your MP3 files into full-sized CD tracks and then save them to an audio CD. This allows you to listen to your MP3 files on any CD player. But remember that converting MP3 files into CD tracks limits the number of files you can fit on a CD. Also, converting an MP3 into a larger file format doesn't replace the information lost during the original MP3 encoding. In other words, the music files won't sound any better than they did as MP3 files.

Many MP3 encoders have plug-ins that create full-size WAV files from MP3 files, and some of the encoders will also decode. Once you have the full-size CD tracks, then the software that comes with your CD-R drive will let you create an audio CD easily. Other MP3 encoders and players have similar features. It's good to do a little research before you choose your MP3 application -- some are more reliable than others.
The CD-Recordable FAQ is an excellent source of information on getting data and music onto a CD.
If you are an artist who is recording music at home or in a small studio, you can use MP3 files and the Web to distribute your music to a larger audience. The first step is to create a song, either on a cassette tape, minidisc or CD. If it's on a CD, you can use the ripper and encoder tools described in the previous section to create an MP3 file. If it's on a cassette or other source, you can connect the output of the audio source to the line-in or microphone jack of your sound card and record the music digitally on your computer. Then you can encode that file to create the MP3.
Once you have an MP3 file in hand, you have two distribution options:

• You can go to an MP3-distribution site and let them distribute your music. The advantage of this approach is that large MP3-distribution sites gets millions of visitors every month, so your potential audience is very large.
• You can create your own Web site for your music or band and promote the site yourself. This gives you more control and individuality, but requires you to get the word out on your own. See How Web Pages Work for details on creating and hosting your own Web site.

Some musicians distribute their music through a blog. Jonathan Coulton, known for his comedic folk songs, uses a blog to keep his fans informed of what's going on in his life. They can also find links to purchase his music or listen to several of his songs for free. Coulton's success with this untraditional approach may inspire other musicians to follow suit.
One good option is to make your MP3 files available on a large Web site and then link to the download area from your band's Web site. This lets you get the best of both worlds, and you can take advantage of the larger site's servers for those big MP3 files.

At its peak, Napster was perhaps the most popular Web site ever created. In less than a year, it went from zero to 60 million visitors per month. Then it was shut down by a court order because of copyright violations, and wouldn't relaunch until 2003 as a legal music-download site. The original Napster became so popular so quickly because it offered a unique product -- free music that you could obtain nearly effortlessly from a gigantic database. You no longer had to go to the music store to get music. You no longer had to pay for it. You no longer had to worry about cueing up a CD and finding a cassette to record it onto. And nearly every song in the universe was available.
Given that it was distributing an illegal product, the original Napster's key weakness lay in its architecture -- the way that the creators designed the system. When the courts decided that Napster was promoting copyright infringement, it was very easy for a court order to shut the site down.
The fact that Napster promoted copyright violations did not matter to its users. Most of them have turned to a new file-sharing architecture known as Gnutella. In this article, you will learn about the differences between Gnutella and the old Napster that allow Gnutella to survive today despite a hostile legal environment.

The New Napster Napster was relaunched by new parent company Roxio in 2003. It is now a legal, pay-for-music site -- no copyright infringement in Napster version 2.

On the Web as it is normally implemented, there are Web servers that hold information and process requests for that information (see How Web Servers Work for details). Web browsers allow individual users to connect to the servers and view the information. Big sites with lots of traffic may have to buy and support hundreds of machines to support all of the requests from users. Napster pioneered the concept of peer-to-peer file sharing. With the old version of Napster (Napster relaunched itself in 2003 as a legal, pay-for-music site), individual people stored files that they wanted to share (typically MP3 music files) on their hard disks and shared them directly with other people. Users ran a piece of Napster software that made this sharing possible. Each user machine became a mini server.

If you logged into the old Napster to download a song, here's what happened:

1. You started the Napster software on your machine. Your machine became a small server able to make files available to other Napster users.
2. Your machine connected to Napster's central servers. It told the central servers which files were available on your machine. So the Napster central servers had a complete list of every shared song available on every hard disk connected to Napster at that time.
3. You typed in a query for a song. Let's say you were looking for the song "Roxanne" by The Police. Napster's central servers listed all of the machines storing that song.
4. You picked a version of the song from the list.
5. Your machine connected to the user's machine that had that song, and downloaded the song directly from that machine.

The creator of Napster had a couple of reasons for this approach:

• Napster eventually grew to have billions of songs available. There is no way a central server could have had enough disk space to hold all the songs, or enough bandwidth to handle all the requests.
• Napster was trying to take advantage of a loophole in copyright law that allows friends to share music with friends. The legal concept behind Napster was, "All of these people are sharing the songs on their hard disks with their friends." The courts did not agree with that logic, but it gave Napster enough time to prove the concept and grow to massive size.

This approach worked great and made fantastic use of the Internet's architecture. By spreading the load for file downloading across millions of machines, Napster accomplished what would have been impossible any other way. The central database for song titles was Napster's Achilles' heel. When the court ordered Napster to stop the music, the absence of a central database killed the entire original Napster network.
With the original Napster gone, what you had at that point was something like 100 million people around the world hungry to share more and more files. It was only a matter of time before another system came along to fill the gap.


Currently, the most popular system for sharing files is another peer-to-peer network called Gnutella, or the Gnutella network. There are two main similarities between Gnutella and the old Napster:

• Users place the files they want to share on their hard disks and make them available to everyone else for downloading in peer-to-peer fashion.
• Users run a piece of Gnutella software to connect to the Gnutella network.

There are also two big differences between Gnutella and the old Napster:

• There is no central database that knows all of the files available on the Gnutella network. Instead, all of the machines on the network tell each other about available files using a distributed query approach.
• There are many different client applications available to access the Gnutella network.

Because of both of these features, it would be difficult for a simple court order to shut Gnutella down. The court would have to find a way to block all Gnutella network traffic at the ISP and the backbone levels of the Internet to stop people from sharing.

The original Napster had one piece of "client software" -- the software that users ran on their machines to access the Napster servers. Gnutella has dozens of clients available. Some of the popular Gnutella clients include:

• BearShare
• Gnucleus
• LimeWire
• Morpheus
• WinMX
• XoloX

How a Gnutella client finds a song
Given that there is no central server to store the names and locations of all the available files, how does the Gnutella software on your machine find a song on someone else's machine? The process goes something like this:

• You type in the name of the song or file you want to find.
• Your machine knows of at least one other Gnutella machine somewhere on the network. It knows this because you've told it the location of the machine by typing in the IP address, or because the software has an IP address for a Gnutella host pre-programmed in. Your machine sends the song name you typed in to the Gnutella machine(s) it knows about.
• These machines search to see if the requested file is on the local hard disk. If so, they send back the file name (and machine IP address) to the requester.
• At the same time, all of these machines send out the same request to the machines they are connected to, and the process repeats.
• A request has a TTL (time to live) limit placed on it. A request might go out six or seven levels deep before it stops propagating. If each machine on the Gnutella network knows of just four others, that means that your request might reach 8,000 or so other machines on the Gnutella network if it propagates seven levels deep.

It is an extremely simple and clever way of distributing a query to thousands of machines very quickly.
This approach has one big advantage -- Gnutella works all the time. As long as you can get to at least one other machine running Gnutella software, you are able to query the network. No court order is going to shut this system down, because there is no one machine that controls everything. However, Gnutella has at least three disadvantages:

• There is no guarantee that the file you want is on any of the 8,000 machines you can reach.
• Queries for files can take some time to get a complete response. It might be a minute or more before all of the responses, seven levels deep, come in.
• Your machine is part of this network. It is answering requests and passing them along, and in the process routing back responses as well. You give up some amount of your bandwidth to handle requests from all the other users.

Apparently, these disadvantages are minor, because people have downloaded hundreds of millions of copies of Gnutella clients.

XoloX is a typical, fairly simple program for connecting into the Gnutella network. It does not have some of the bells and whistles of the more sophisticated clients, but it does work, it is a small file to download (only 600 kilobytes or so), it has no "spyware" or bundled pop-up advertising mixed in with it, and it is very easy to install and use. Its simplicity makes it useful to demonstrate how a typical Gnutella client works.
There are three big things you can do with XoloX: search for files, transfer files to your machine and look at your downloaded files. There are three buttons at the top of the XoloX window that let you toggle between these three activities.
The figure above shows a typical screenshot during a search. All you do is type in the name (or keywords) of the file you are looking for. You can also select the file type: audio, video, etc., or "All Types." Your XoloX client sends out a message containing your search string, and over the course of 30 to 60 seconds a search window fills with results from the thousands of other machines that are processing your query.
One thing you will notice in the search window is a score. The score represents the number of machines currently online that have the same file available. By choosing a file with a high score, you increase your odds of actually getting the file you want.


To download a file, you simply double-click it in the search window. This sends the file name to the Transfer window. Once a filename is in the transfer window, your copy of XoloX will connect to the peer machine to download the file. One nice thing about XoloX/Gnutella is that if multiple machines have the file available, your client can connect to several of them simultaneously to download the file very quickly. In the figure below, you can see that Filename1.avi in particular is taking advantage of this capability to download the file at a rate of 69.2 kilobytes per second. XoloX is estimating 43 minutes to complete the download of over 100 megabytes.
When you pick a file for downloading, it is fairly common for nothing to happen. That is, XoloX cannot connect to the machine that has the file, or the machine holding the file is already busy helping other people. You can solve this problem either by waiting (eventually a busy machine can get unbusy), by choosing files with high scores (increasing the likelihood of finding an unbusy machine), or by deleting a file that is going nowhere from the transfer window and replacing it with an identical file from the search window.
Once you have the files on your machine, you can find them in a XoloX directory and in the Files window of XoloX. You can share all the files you've downloaded with other people if you like. You do this by first specifying the directories and file types you want to share in the Preferences dialog:

You can also control how much outgoing bandwidth you allow XoloX to consume when people download files from you:

This can keep people from chewing up all your upstream bandwidth.


Gnutella itself is legal. There is no law against sharing public domain files. It's when people use Gnutella to distribute copyrighted music and films that its use becomes illegal. This is the problem that got Napster in trouble. The music industry is officially upset about Gnutella, but there is currently no easy way to control it. Attacking the Gnutella architecture is one way to disrupt file-sharing activities. There are currently two approaches being used:

1. Overloading the Gnutella network with a flood of bogus search packets.
2. Filling Gnutella servers with corrupted files.

Gnutella's many developers have adapted to problems in the past, so it is probable that new software can work around these threats and keep the files flowing. The debate at the moment is how much financial damage file-sharing actually causes. Is a shared file a theft, or is it a form of free advertising and exposure just like airtime on the radio is?

If you have read the HSW article entitled How MP3 Files Work, then you are familiar with the MP3 format for digital music. You know that you can download MP3 files from the Internet and play them on your computer, listen to them on a portable MP3 player or even burn your own CDs. The advantage of the MP3 format is that it makes song files small enough to move around on the Internet in a reasonable amount of time. The initial MP3 craze was fueled by sites like mp3.com. On these sites, anyone can upload a song. However, the sites cannot legally store or distribute copyrighted material -- that would be copyright infringement, which is illegal. So all of the songs that you find on mp3.com (and sites like it) are either public domain songs, songs uploaded by artists who are trying to get exposure, or songs released by record companies trying to build interest in a CD.
Napster is a different way to distribute MP3 files. Instead of storing the songs on a central computer, the songs live on users's machines. When you want to download a song using Napster, you are downloading it from another person's machine, and that person could be your next door neighbor or someone halfway around the world. Individuals tend to be less concerned about copyright laws than businesses like mp3.com have to be, so individuals make all sorts of copyrighted songs available to the world from their personal machines. This means that anyone can download, for free, any song that someone has taken the time to encode in the MP3 format.
Right now the biggest users of Napster are college students. There are four reasons for this trend:

• College students tend to like music
• Colleges and Universities have spent lots of money making high-speed Internet access and computers available to students
• College students tend to be comfortable with technologies like MP3
• College students tend to have little money

Therefore the idea of downloading music for free is appealing and easy for students. The problem with Napster is that it is a big, automated way to illegally copy copyrighted material. This is why there is so much emotion around it right now. College students love Napster because they can get music for free instead of paying $15 for a CD. The music industry is against Napster because people can get music for free instead of paying $15 for a CD. Napster's defense is that the files are personal files that people maintain on their own machines, and therefore they are not responsible. But it is a fact that thousands of people are making thousands of copies of copyrighted songs, and neither the music industry nor the artists get any money in return for those copies. That is copyright infringement, and is why Napster has ended up in court.
How this plays out will be extremely interesting to watch. Copyright law has been in place for hundreds of years and works very well. George Lucas has created four Star Wars films, for example, and knows that he will be adequately rewarded for creating more under the current law. However, Internet technology is changing everything, and may create completely new ways for artists to get paid that are comfortable for both artists and fans. If you can invent a comfortable way for any artist to get paid when people view/hear his or her work, you will be a very famous person! You will also enhance the creative process.

If you spend much time online, then you have most likely heard of Napster. What began in 1999 as an idea in the head of a teenager proceeded to redefine the Internet, the music industry and the way we all think about intellectual property. Napster is now back in business as a legal, pay-per-song music-download site; but it once was a controversial service that spurred what is still one of the greatest Internet-related debates: Just because we can get the music we want without paying for it, should we?

In this article, you will learn what the original Napster was, what it did and how it worked. You will also learn why there is so much concern, particularly in the music industry, about the issues of copyright and intellectual property.

If you have read How MP3 Files Work, then you are familiar with the MP3 format for digital music. You know that you can download MP3 files from the Internet and play them on your computer, listen to them on a portable MP3 player or even burn your own CDs. The advantage of the MP3 format is that it makes song files small enough to move around on the Internet in a reasonable amount of time.

Choosing an MP3 player... If you're looking for a portable music player, there are a ton of options. Check out the reviews at Consumer Guide Products for more information.

The initial MP3 craze was fueled by sites like MP3.com. On these sites, anyone can upload a song. The songs are then stored on a server that is part of the Web site. Other users can connect to the Web site and download songs they are interested in. Another way of obtaining MP3 files is to perform a search on the title or artist that you are looking for. Quite often, the search would return a lot of links that were broken, meaning that the Web page could not be found. In early 1999, Shawn Fanning began to develop an idea as he talked with friends about the difficulties of finding the kind of MP3 files they were interested in. He thought that there should be a way to create a program that combined three key functions into one. These functions are:

• Search engine: Dedicated to finding MP3 files only
• File sharing: The ability to trade MP3 files directly, without having to use a centralized server for storage
• Internet Relay Chat (IRC): A way to find and chat with other MP3 users while online

Fanning, only 18 at the time, spent several months writing the code that would become the utility Napster. He uploaded the original beta version to download.com, where it quickly became one of the hottest downloads on the site. Shawn knew he had stumbled on to something big.
Napster (Napster was Fanning's nickname in high school, because of his hair) is a different way to distribute MP3 files. Instead of storing the songs on a central computer, the songs live on users' machines. This is called peer-to-peer sharing, or P2P. When you want to download a song using Napster, you are downloading it from another person's machine, and that person could be your next-door neighbor or someone halfway around the world. (See How Gnutella Works to learn more.)
Let's take a look at what was necessary for you to download a song that you are interested in using the old Napster.com: You needed:

• A copy of the Napster utility installed on your computer
• A directory on your computer that has been shared so that remote users can access it
• Some type of Internet connection

The provider of the song needed:

• A copy of the Napster utility installed on his computer
• A directory on his computer that has been shared so that someone else could access it
• Some type of Internet connection that was "on"
• A copy of the song in the designated, shared directory

Here is what happened when you decided to look for the song:

1. You opened the Napster utility.
2. Napster checked for an Internet connection.
3. If it found a connection, Napster logged you onto the central server. The main purpose of this central server was to keep an index of all the Napster users currently online and connect them to each other. It did not contain any of the MP3 files.
4. You typed in the title or artist of the song you were looking for.
5. The Napster utility on your computer queried the index server for other Napster computers online that had the song you requested.
6. Whenever a match was found, the Napster server informed your computer where to find the requested file.
7. When the server replied, Napster built a list of these systems in the results window.
8. You clicked on the file(s) that interested you and then chose Download.
9. Your copy of Napster attempted to establish a connection with the system hosting the file you selected.
10. If a connection wa successfully made, the file began downloading.
11. Once the file wa downloaded, the host computer broke the connection with your system.
12. You opened up your MP3 player software and listened to the song.

The problem that the music industry had with Napster was that it was a big, automated way to copy copyrighted material. It is a fact that thousands of people were, through Napster, making thousands of copies of copyrighted songs, and neither the music industry nor the artists got any money in return for those copies. (This type of piracy is still happening now, through sites other than Napster.) This is why there was so much emotion around it. Many people loved Napster because they could get music for free instead of paying $15 for a CD. The music industry was against Napster because people could get music for free instead of paying $15 for a CD. Napster's defense was that the files were personal files that people maintained on their own machines, and therefore Napster was not responsible. Individuals tend to be less concerned about copyright laws than businesses have to be, so individuals make all sorts of copyrighted songs available to the world from their personal machines. This means that anyone can download, for free, any song that someone has taken the time to encode in the MP3 format.
Even though Napster was banned from about 40 percent of U.S. colleges and universities when it was operating in its illegal form, some of the biggest users of Napster were college students. There are several reasons for this:

• College students tend to like music.
• Colleges and universities have spent lots of money making high-speed Internet access and computers available to students.
• College students tend to be comfortable with technologies like MP3.
• College students tend to have little money.

These things make the idea of downloading music for free appealing and easy for students. Sites cannot legally store or distribute copyrighted material without permission -- that would be copyright infringement, which is illegal. In fact, MP3.com was sued by the record companies because the company did have copyrighted materials available online for purchase without permission of the copyright holders, even though MP3.com was paying royalties for everything sold. Songs that you find on legal download sites are:

• In the public domain
• Uploaded by artists who are trying to get exposure
• Released by record companies trying to build interest in a CD
• Paid for by you for the right to download, and the site pays the artist and/or record company royalties

An item that added to the controversy was the Audio Home Recording Act of 1992. This law provides the buyer of a CD or cassette with the right to not only make a copy for their own personal use, but also to make copies for friends as long as the original owner is not selling the copies or receiving any other type of compensation. Napster fans said that what they are doing was perfectly legal since the law does not specify who those friends must be or how many of them you can give a copy to.
The simple fact is that P2P is here to stay, regardless of legality disputes. Since the introduction of Napster, many other similar utilities and Web sites have appeared. And most of them do not limit file sharing to just MP3s as Napster did. Some, like Gnutella, allow virtually anything to be shared. Another feature of some of these P2P utilities is the elimination of the need for a central index server. In true peer-to-peer fashion, these utilities search each other out online. For example, as soon as a Gnutella client comes online, it says "Hello, I'm here" to another Gnutella client. That client then tells eight other clients that it has already established contact with the new one. Each of those eight then tell seven others, who tell six others and so on. This way, each client has a larger number of other clients who know it is online and what content it has available.
P2P utilities that employ this decentralized approach are virtually impossible to shut down. Since there is no central server maintaining the index of users, there is no easy way to target and stop the use of the program. Many of the content developers in music, video and other industries are beginning to realize that fundamental changes in the way royalties and licensing work are vital to keep up with the revolutionary world of the Internet.
Probably the biggest question that most people have about Napster is, "How did they make money?" The short answer is, "They didn't." Initially, Napster was not intended to be a revenue-generating business. Like many great inventors before, Shawn Fanning created the program to see if it could be done, not because of money. But even he had no idea how big it would become.

With all the recent Napster news in the newspapers and television, the recent availability of Aimster may be of interest to people who want to share files. Aimster leverages the popularity of AOL's Instant Messenger (AIM). Your instant message buddies can help by recommending files without the hassles of e-mail. Aimster lets you share files only with those you already know and trust -- those on your buddy list. It is more manageable and relatively limited compared to Napster. You share files only with those you choose from your AIM buddy list. AIM users do not have to be AOL users.
The Next Killer Application?
Aimster users may not have the legal worries of Napster, since you have more control over your files. All of the reported 50 to 60 million Napster users have access to your files while you are connected to a Napster node. Aimster users can only search or be searched by others who are on their AIM buddy list. Instant file sharing may be the next killer application, allowing people to share their artwork, photos, recipes and other creative items.