DNS

Introduction:

In the vast world of the internet, where millions of websites are just a click away, have you ever wondered how your browser knows where to find the website you want to visit? The answer lies in the Domain Name System (DNS), a fundamental component of computer networking and the backbone of internet addressing.
What is DNS?
The Domain Name System (DNS) is a hierarchical decentralized naming system that translates human-readable domain names into machine-readable IP addresses. It acts as a directory for the internet, allowing users to access websites using easily memorable domain names instead of complex IP addresses.

DNS Architecture:

The DNS architecture consists of several components that work together to ensure smooth and efficient communication between computers on the internet. Let’s take a closer look at these components:

DNS Resolver: When you enter a domain name in your browser, the DNS resolver is responsible for initiating the DNS lookup process. It sends a query to the DNS server to retrieve the corresponding IP address for the given domain name.

DNS Server: DNS servers are the backbone of the DNS system. They store and manage the database of domain names and their corresponding IP addresses. There are several types of DNS servers, including authoritative DNS servers, recursive DNS servers, and caching DNS servers.

Authoritative DNS Server: This type of DNS server holds the official records for a particular domain. When a DNS resolver queries an authoritative DNS server, it provides the most accurate and up-to-date information about the requested domain name.

Recursive DNS Server: These servers handle DNS queries by recursively querying other DNS servers until they find the requested IP address. They store the results of previous queries in their cache to speed up future lookups.

Caching DNS Server: Caching DNS servers store recently accessed DNS records in their cache. When a DNS resolver queries a caching DNS server, it first checks if the requested information is available in its cache. If not, it will query other DNS servers and store the results for future use.

DNS Resolution Process:

When you enter a domain name in your browser, the DNS resolution process begins. Here’s a simplified step-by-step explanation of how it works:

Your computer sends a DNS query to the DNS resolver, usually provided by your internet service provider (ISP).

The DNS resolver checks its cache to see if it has the IP address corresponding to the domain name. If not, it sends a query to the recursive DNS server.

The recursive DNS server checks its cache and sends a query to the authoritative DNS server responsible for the requested domain.

The authoritative DNS server responds with the IP address, and the recursive DNS server passes it back to the DNS resolver.

The DNS resolver stores the IP address in its cache and sends it back to your computer.

Your computer now knows the IP address of the requested domain and can establish a connection to the server hosting the website.

 

Links

Code Examples

C#
using System.Net;

IPAddress[] addresses = Dns.GetHostAddresses("example.com");
foreach (IPAddress address in addresses)
{
    Console.WriteLine(address.ToString());
}

JavaScript
const dns = require('dns');

dns.resolve4('example.com', (err, addresses) => {
  if (err) throw err;

  addresses.forEach((address) => {
    console.log(address);
  });
});

Python
import socket

addresses = socket.getaddrinfo('example.com', None)
for address in addresses:
    print(address[4][0])

PHP
$hostname = "example.com";
$ip = gethostbyname($hostname);
echo $ip;

Conclusion