What Do Web Browsers Use to Locate Things?
Web browsers need two things to locate resources over the Internet. They are both addresses. A URL is a Uniform Resource Locator and this is the name for the full address of a Web page. The other address is the IP address. This address is defined by the Internet Protocol. It is unique throughout the world and identifies a particular computer. The URL and the IP address are linked by the Domain Name System.
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Uniform Resource Locator
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The URL is the address the user sees in the address bar of the Web browser. It has five elements, only two of which are essential. First of all, a code for the operating transfer protocol starts the URL. This is either HTTP, which is the Hypertext Transfer Protocol, HTTPS, the Hypertext Transfer Protocol Secure system, or FTP, the File Transfer Protocol. The next element of the URL is the domain name. This is the most important part of a Web address. No Web browser can reach a Web site by its URL. These addresses are fronts for the real underlying address, which is the IP address. The Web address is a system that humans are better able to read and remember. The final three elements are the directory path on the site, the required file name and then any parameters needed to activate the file.
Domain Name
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Domain names make the Internet commercially viable. A domain name is like a sign on a shop. No physical shop advertises itself by its address. Similarly, businesses on the Web do not advertise themselves by their IP address. A domain name can be snappy and memorable. Unfortunately, domain names as character strings are not as precise as numbers for addressing. Words can be spelled in different ways, numbers are unequivocal.
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IP Address
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Every computer in the world connected to the Internet has a unique IP address. Not only does a domain name not provide an address for a server, but a server may host many Web addresses. The IP address is a 32 digit binary number. To be easier for humans to manage that number is divided into four eight bit sections. Eight bits form a byte, and so an IP address uses four bytes. Each byte is converted to a digital number and then the four numbers of the address are separated by dots. This representation is called "dot notation." Thus, an IP address looks like "123.43.23.10."
Domain Name System
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A user types a URL into the address box of a Web browser. This URL contains a file name located at a domain. However, the Web browser does not know how to reach that domain, because it is just a name and not a proper address. The browser's first port of call is to the Domain Name System. The Domain Name System, or DNS is also called the Domain Name Service. It maintains a number of servers throughout the world listing domain names and giving the IP address for each. The browser goes to the server for the domain and retrieves the IP address. With this it can contact the Web server at that IP address and request the file given in the URL.
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References
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