Packet, Packet, Who's Got the Packet?
In order to retrieve this article, your computer had to connect with the Web server containing the article's file. We'll use that as an example of how data travels across the Internet.
First, you open your Web browser and connect to our Web site. When you do this, your computer sends an electronic request over your Internet connection to your Internet service provider (ISP). The ISP routes the request to a server further up the chain on the Internet. Eventually, the request will hit a domain name server (DNS).
This server will look for a match for the domain name you've typed in (such as www.howstuffworks.com). If it finds a match, it will direct your request to the proper server's IP address. If it doesn't find a match, it will send the request further up the chain to a server that has more information.
The request will eventually come to our Web server. Our server will respond by sending the requested file in a series of packets. Packets are parts of a file that range between 1,000 and 1,500 bytes. Packets have headers and footers that tell computers what's in the packet and how the information fits with other packets to create an entire file. Each packet travels back up the network and down to your computer. Packets don't necessarily all take the same path -- they'll generally travel the path of least resistance.
That's an important feature. Because packets can travel multiple paths to get to their destination, it's possible for information to route around congested areas on the Internet. In fact, as long as some connections remain, entire sections of the Internet could go down and information could still travel from one section to another -- though it might take longer than normal.
When the packets get to you, your device arranges them according to the rules of the protocols. It's kind of like putting together a jigsaw puzzle. The end result is that you see this article.
This holds true for other kinds of files as well. When you send an e-mail, it gets broken into packets before zooming across the Internet. Phone calls over the Internet also convert conversations into packets using the voice over Internet protocol (VoIP). We can thank network pioneers like Vinton Cerf and Robert Kahn for these protocols -- their early work helped build a system that's both scalable and robust.
That's how the Internet works in a nutshell. As you look closer at the various devices and protocols, you'll notice that the picture is far more complex than the overview we've given. It's a fascinating subject -- learn more by following the links below.
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More Great Links
- Computer History Museum "Computer Pioneer Robert Kahn with Ed Feigenbaum." YouTube. Jan. 9, 2007. (April 23, 2010)http://www.youtube.com/watch?v=t3uTKs9XZyk
- Congressional Digest. "Internet History: From ARPANET to Broadband." February 2007. pp. 35 - 37, 64.
- Hauben, Ronda. "From the ARPANET to the Internet." Columbia University. June 23, 1998. (April 26, 2010) http://www.columbia.edu/~rh120/other/tcpdigest_paper.txt
- Information Sciences Institute. "Internet Protocol." September 1981. (April 26, 2010) http://www.ietf.org/rfc/rfc791.txt
- Opus One. "What is IPv6?" (April 27, 2010) http://www.opus1.com/ipv6/whatisipv6.html
- THINK project. "A Technical History of the ARPANET." The University of Texas at Austin. (April 26, 2010) http://userweb.cs.utexas.edu/users/chris/nph/ARPANET/ScottR/arpanet/index.htm