Write a short note on Domain Name System (DNS).

The Domain Name System (DNS) is a hierarchical and decentralized system that translates human-readable domain names, like “example.com,” into IP addresses used for identifying devices on a network. This system is fundamental for the functioning of the internet, as it allows users to use intuitive website names instead of having to remember numeric IP addresses.

The process works as follows: when a user enters a domain name into a web browser, the browser sends a query to a DNS resolver. The resolver then asks a series of DNS servers, starting with the root servers, followed by the Top-Level Domain (TLD) servers, and finally, the authoritative name servers for the specific domain, until it receives the corresponding IP address. Once the IP address is obtained, the browser can then request the website’s content from the server at that address.

DNS also supports other functionalities, like mail exchange and text records. Moreover, it’s crucial for DNS data to be accurate and available; hence, a distributed database system is used, spreading the information across many servers worldwide. This decentralized structure also enhances the resilience and scalability of the internet.

However, like any system, DNS has vulnerabilities. Issues like DNS cache poisoning can misdirect users to malicious websites, so various security measures, such as DNSSEC (DNS Security Extensions), have been developed to counter these threats.