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How DNS Works_v2

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This is one of my tutorials originally published at xmodulo.com

Domain Name System (DNS) is one of the most critical services in the Internet. Without DNS, we would not be able to access the web. Before going into the details on how DNS works, a little on the background may be helpful.

When you are accessing, say, Google, your traffic originates from your computer, goes through the backbone of your ISP, and then their own upstream provider and so on; until it reaches Google's network. In the TCP/IP-based current Internet, the transit communication from your computer all the way to Google's network is driven by a set of intermediate routers based on the IP address of the destination web server of Google.

This means we need to know the IP address of Google's web server to access Google service. However, it is almost impossible for us to keep more than hundreds of IP addresses in our memory. What if there could be a mechanism to map IP addresses to domain names t…