5. The Domain Name System

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The Domain Name System lets you access websites by their domain name like (www.khanacademy.org), so you don’t have to keep a list of numeric Internet Protocol (IP) addresses like “212.78.1.25”. IP address are determined by where your computer connects to the Internet. When you have a portable

computer and you move from one location to another, you get a new IP address at each new location. Since no one connects to your portable computer, it does not matter if your IP address changes from time to time. But since so many people connect to a web server, it would be inconvenient if the server moved to a new location and needed to change its IP address.

When your computer makes a connection to a system using a domain name address, the first thing your computer does is look up the IP address that corresponds to the domain name. Then your computer makes the connection using the IP address.

Adding the separate step of looking up the IP address for a DNS address also makes it easier to move a server from one location to another. The server is given a new IP address and the entry for the domain address is updated. Once the DNS entry is updated, new requests for the domain name are given the new IP address.

Since end users access most servers using domain names and never see the IP address, a server can be moved to a new network connection without affecting the end user’s ability to access the server.

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