Understanding the Domain Name System
The Domain Name System (DNS) is the backbone of the internet. It translates human-readable domain names like sillyhost.co.uk into numerical IP addresses like 185.52.0.1 that computers use to communicate with each other.
How DNS Works
When you type a domain name into your browser, the following process occurs:
- Browser cache check: Your browser first checks if it already knows the IP address from a previous visit.
- Operating system cache: If not cached in the browser, your computer's OS checks its own DNS cache.
- Recursive resolver: If still not found, the request goes to your ISP's DNS resolver (or a public one like Cloudflare's
1.1.1.1). - Root nameservers: The resolver queries a root nameserver, which directs it to the correct TLD nameserver (e.g., the
.comservers). - TLD nameservers: The TLD server responds with the authoritative nameserver for the specific domain.
- Authoritative nameserver: This server holds the actual DNS records and returns the IP address.
- Response delivered: The IP address is returned to your browser, which connects to the web server.
Key DNS Record Types
- A Record: Maps a domain to an IPv4 address.
- AAAA Record: Maps a domain to an IPv6 address.
- CNAME Record: Creates an alias from one domain to another.
- MX Record: Directs email to the correct mail server.
- TXT Record: Stores text data, commonly used for email authentication (SPF, DKIM, DMARC).
- NS Record: Specifies which nameservers are authoritative for the domain.
- SRV Record: Defines the location of specific services like SIP or XMPP.
Why DNS Matters
Correct DNS configuration is essential for your website to load, your emails to be delivered, and your online services to function. Misconfigured DNS records are one of the most common causes of website and email downtime.