DNS | How DNS Works

The Domain Name System (DNS) is the phonebook of the Internet. Humans access information online through domain names, like www.topperskills.com. Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP addresses so browsers can load Internet resources.

Each device connected to the Internet has a unique IP address which other machines use to find the device. DNS servers eliminate the need for humans to memorize IP addresses such as 192.168.1.1 (in IPv4), or more complex newer alphanumeric IP addresses such as 2400:cb00:2048:1::c629:d7a2 (in IPv6).

The Domain Name System (DNS) is a distributed directory that resolves human-readable hostnames, such as www.dyn.com, into machine-readable IP addresses like 50.16.85.103. DNS is also a directory of crucial information about domain names, such as email servers (MX records) and sending verification (DKIM, SPF, DMARC), TXT record verification of domain ownership, and even SSH fingerprints (SSHFP).

1. A user opens a web browser, enters www.topperskills.com in the address bar, and presses Enter.

2. The request for www. topperskills.com is routed to a DNS resolver, which is typically managed by the user's Internet service provider (ISP), such as a cable Internet provider, a DSL broadband provider, or a corporate network.

3. The DNS resolver for the ISP forwards the request for www. topperskills.com to a DNS root name server.

4. The DNS resolver for the ISP forwards the request for www. topperskills.com again, this time to one of the TLD name servers for .com domains. The name server for .com domains responds to the request with the names of the four Amazon Route 53 name servers that are associated with the topperskills.com domain.

5. The DNS resolver for the ISP chooses an Amazon Route 53 name server and forwards the request for www. topperskills.com to that name server.

6. The Amazon Route 53 name server looks in the topperskills.com hosted zone for the www. topperskills.com record, gets the associated value, such as the IP address for a web server, 192.0.2.44, and returns the IP address to the DNS resolver.

7. The DNS resolver for the ISP finally has the IP address that the user needs. The resolver returns that value to the web browser. The DNS resolver also caches (stores) the IP address for topperskills.com for an amount of time that you specify so that it can respond more quickly the next time someone browses to topperskills.com. For more information, see time to live (TTL).

8. The web browser sends a request for www. topperskills.com to the IP address that it got from the DNS resolver. This is where your content is, for example, a web server running on an Amazon EC2 instance or an Amazon S3 bucket that's configured as a website endpoint.

9. The web server or other resource at 192.0.2.44 returns the web page for www. topperskills.com to the web browser, and the web browser displays the page.