What is DNS and How it Works

What is Domain Name System (DNS)?

DNS (Domain Name System) is a hierarchical and decentralized naming system used to translate human-readable domain names (like www.example.com) into IP addresses (like 192.0.2.1) that computers use to identify each other on the network. Essentially, DNS is the internet’s phonebook.

How DNS Works

Domain Name Resolution: When you enter a domain name into your web browser, a DNS query is initiated to find the corresponding IP address.

DNS Query Process:

– Local DNS Cache Check: First, the system checks if the IP address for the requested domain is stored in the local cache. If found, the process ends here.
– Recursive DNS Resolver: If not found locally, the query is sent to a recursive DNS resolver (often provided by your ISP or a third-party service like Google DNS or Cloudflare DNS).

Iterative Query to Root DNS Servers:

Root Servers: The recursive resolver queries one of the root DNS servers. Root servers don’t know the final IP address but can direct the query to the appropriate top-level domain (TLD) server (like .com, .org, .net).

TLD DNS Servers:

The query is forwarded to the TLD server, which provides the address of the authoritative DNS server for the specific domain (like example.com).

Authoritative DNS Servers:

The recursive resolver then queries the authoritative DNS server for the domain. This server holds the actual IP address for the requested domain.

Response to the Client:

The authoritative DNS server responds with the IP address to the recursive resolver, which then returns the IP address to the user’s device.

Connection to the Server:

With the IP address obtained, the web browser can now connect to the web server hosting the domain and request the desired webpage.

Example of DNS Resolution

User enters www.example.com in the browser.
The local system checks its cache.
If not found, the query goes to the recursive resolver.
The resolver queries a root server.
The root server directs it to the .com TLD server.
The TLD server points to the authoritative DNS server for example.com.
The authoritative server returns the IP address (e.g., 192.0.2.1).
The resolver sends this IP address back to the user’s browser.
The browser connects to the server at 192.0.2.1 and loads the website.

Conclusion

DNS is essential for the user-friendly operation of the internet, allowing us to use memorable domain names instead of numeric IP addresses. By translating domain names into IP addresses through a hierarchical query process, DNS ensures efficient and accurate connections between users and web resources.

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