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What is a DNS Resolver?

Published in Networking Basics 3 mins read

A DNS resolver is a service that translates domain names into IP addresses, enabling your computer to connect to websites and other online services.

Understanding the DNS Resolver Role

The Domain Name System (DNS) is like the internet's phonebook. When you type a website address (like www.example.com) into your browser, your computer needs to find the IP address associated with that domain to connect to the server hosting the website. This is where the DNS resolver comes into play.

How a DNS Resolver Works

Here's a breakdown of the process:

  • Request: Your device sends a request for the IP address of a domain name to a DNS resolver.
  • Lookup: The DNS resolver then searches its cache or queries other DNS servers to locate the IP address.
  • Response: Once the IP address is found, the DNS resolver sends it back to your device.
  • Connection: Your device uses the IP address to connect to the web server hosting the website.

As defined in the internet specification document RFC 1034, DNS resolvers are "programs that extract information from name servers in response to client requests."

Types of DNS Resolvers

There are primarily two types of DNS resolvers:

  1. Recursive Resolver: This is the resolver your device typically uses. It performs the full query process on your behalf to find the IP address. These are often provided by your Internet Service Provider (ISP), Google, Cloudflare, or other DNS service providers.
  2. Non-Recursive Resolver (Authoritative Name Server): This type of server contains the actual DNS records for a specific domain. Recursive resolvers query authoritative name servers to resolve domain names.

Importance of DNS Resolvers

DNS resolvers are essential for several reasons:

  • User Convenience: They allow users to access websites using human-readable domain names instead of complicated IP addresses.
  • Internet Accessibility: Without DNS resolvers, navigating the internet would be nearly impossible.
  • Efficiency: Caching mechanisms used by resolvers reduce the time it takes to resolve a domain name repeatedly.

Example

Let's say you want to visit www.example.com. Here's a simplified explanation of how a DNS resolver helps:

  1. You type www.example.com into your browser.
  2. Your computer sends a request to your designated DNS resolver (e.g., your ISP's resolver).
  3. The resolver checks its cache to see if it recently resolved this address. If not, it asks other DNS servers.
  4. The resolver eventually contacts an authoritative name server for example.com.
  5. The authoritative server provides the IP address for www.example.com.
  6. The resolver relays the IP address back to your computer.
  7. Your browser connects to the web server using the IP address, and the website loads.

Conclusion

In summary, a DNS resolver acts as a crucial intermediary, translating domain names into IP addresses and enabling your device to access online resources. It operates behind the scenes, ensuring a seamless web browsing experience for users.

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