The Life of an Internet Request

June 08, 2012

by Web Programmer Richard S. Joswick

Thousands of globally situated computers join forces to bring us the World Wide Web. Specific protocols work together to pinpoint any connected computer anywhere in the world. In brief, what happens when a computer-user enters a web address into their address bar is seen below.

Every computer connected to the Internet must be numerically identified via an Internet Protocol (IP) address (such as 199.187.226.158). Under existing IPv4 (Internet Protocol version 4), available numbers are limited so most requests jump a series of routers. Routers direct traffic among the computers that share its networks and external computers communicating to the same. In most cases, your request will make its way to your Internet Service Provider (ISP), unless you’re communicating directly to a computer on the same network (a Local Area Network (LAN)).

ISPs make up the smallest part of the globe-spanning network comprised of Network Service Providers (NSP) connecting at Internet Exchange Points such as Network Access Points (NAP) and Metropolitan Area Exchanges (MAE).

A packet is any data sent over the Internet. According to the various protocols at play, such as the Hypertext Transfer Protocol (HTTP) and Transmission Control Protocol (TCP), various layers of data are wrapped around the request to describe direction, origin, sequence and more.

But most people don’t send requests directly to IP addresses. People instead use Uniform Resource Locators (such as www.pepsi.com). So what happens? Web addresses are translated to IP addresses by searching a distributed database known as the Domain Name Service (DNS) database. This database tracks computer names and their associated IP addresses. Changes to the DNS database promulgate globally as updates are pushed. This, for instance, can cause a delay when changing web hosts.

This is an involved process even for an army of computers. Caching helps alleviate this issue. Caching refers to storing content closer to home, ideally on your own computer, and referencing the local versions of the files at any opportunity. Since one webpage frequently has additional images, videos, and supporting files, this results in much quicker web browsing. Clearing a browser’s cache forces the browser to send requests and is often helpful when not seeing the updates one would normally expect.

Just as your browser sends the requests, it is also responsible for handling them. Data can be sent back in a compressed format. The browser uncompresses the data, makes additional requests as necessary, and finally presents the information in stages to the user.

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The scope and magnitude of worldwide cooperation that is the Internet is something to be marveled at, even if it is easy to take for granted. From the start of the request to the final media display, many technologies work hand-in-hand to deliver information and entertainment.