Domain Name System (DNS) is a hierarchical, decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide.
Here is a step-by-step explanation of how DNS works:
- A user types a domain name (e.g., www.example.com) into their web browser and hits enter.
- The web browser sends a request to the local DNS resolver to resolve the domain name into an IP address.
- The local DNS resolver checks its cache to see if it has a recent copy of the DNS record for the domain name. If it does, it returns the IP address to the web browser.
- If the local DNS resolver does not have a recent copy of the DNS record, it sends a request to the root DNS server to find out which top-level domain (TLD) server is responsible for the domain name.
- The root DNS server responds with the IP address of the TLD server for the appropriate TLD (e.g., .com).
- The local DNS resolver sends a request to the TLD server to find out which authoritative DNS server is responsible for the domain name.
- The TLD server responds with the IP address of the authoritative DNS server for the domain name.
- The local DNS resolver sends a request to the authoritative DNS server for the domain name.
- The authoritative DNS server responds with the IP address for the domain name.
- The local DNS resolver stores the DNS record (domain name and IP address) in its cache and returns the IP address to the web browser.
- The web browser uses the IP address to send a request for the website to the web server.
- The web server sends the website back to the web browser.
DNS works by using a combination of zones and records. Zones are divisions of the domain name space, and records are the individual entries in those zones. There are several types of DNS records, including A records (which map domain names to IP addresses), CNAME records (which map domain names to other domain names), and MX records (which map domain names to mail servers).
