Definition
Domain Name Server (DNS)
A hierarchical and decentralized system that translates 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 internet.
- When you type a website address into your browser, such as www.example.com, your computer needs to find the IP address associated with that domain name to connect to the correct server.
- The Domain Name System (DNS) acts as a directory that translates human-readable domain names into machine-readable IP addresses.
How DNS Works
Domain Name Resolution
- When you enter a domain name, your computer sends a request to a DNS resolver, usually provided by your internet service provider (ISP).
- The resolver checks its cache to see if it already knows the IP address. If not, it queries other DNS servers to find the answer.
Hierarchical Structure
- DNS is organized in a hierarchical structure with different levels of servers:
- Root Servers : These are at the top of the hierarchy and direct queries to the appropriate Top-Level Domain (TLD) servers (e.g., .com, .org).
- TLD Servers : These servers handle specific domains, such as .com or .net, and direct queries to the authoritative DNS servers for the requested domain.
- Authoritative DNS Servers : These servers hold the actual IP address for the domain and provide the final answer to the query.
Caching
- To improve efficiency, DNS resolvers cache the results of queries for a certain period, known as the Time-to-Live (TTL).
- This reduces the need to repeat the entire query process for frequently visited websites.
Why DNS is Important
- User-Friendly: DNS allows users to access websites using easy-to-remember domain names instead of complex IP addresses.
- Scalability: The hierarchical structure of DNS enables it to handle the vast number of domains on the internet.
- Redundancy: Multiple DNS servers ensure that the system remains reliable and available even if some servers fail.
Hint
DNS is often compared to a phone book for the internet, translating names into numbers that computers can understand.
