DNS: What Is the Domain Name System?

What is DNS?

The DNS (Domain Name System) is a hierarchical, distributed naming system that constitutes one of the foundations of the Internet. Its primary function is to translate domain names — the web addresses that humans memorise easily, like kern-it.be — into numeric IP addresses that servers and routers use to route traffic. Without DNS, users would need to memorise sequences of numbers like 185.199.108.153 to access each website.

Designed in 1983 by Paul Mockapetris (RFC 882 and 883), DNS is a distributed and decentralised system. There is no single DNS server containing all mappings: information is spread across millions of servers worldwide, organised in a domain hierarchy (root, TLD, second-level domains). This distributed architecture ensures system resilience — even if some servers fail, DNS continues to function.

At KERN-IT, DNS management is an essential component of every web project. Whether we are deploying a Wagtail site on a Linux server or configuring a CDN, proper DNS record configuration is the first step to making a site accessible to the world. We manage our clients' DNS zones through reliable providers like Cloudflare or AWS Route 53, ensuring security and performance.

Why DNS Matters

DNS is often overlooked because it works silently in the background. Yet its configuration has a direct impact on your website's availability, performance, security, and SEO.

• Site availability: a DNS configuration error makes your site completely inaccessible. No working DNS, no website. It is the first potential point of failure and the most critical.
• Performance: DNS resolution adds latency to every request. A fast DNS provider (like Cloudflare, whose 1.1.1.1 resolver responds in an average of 11ms) can significantly reduce the initial load time of every page.
• Security: DNS is a common attack vector. DNS spoofing, cache poisoning, and DDoS attacks on DNS infrastructure can redirect traffic or make a site inaccessible. DNSSEC extensions cryptographically sign DNS responses to prevent these attacks.
• Email and deliverability: SPF, DKIM, and DMARC DNS records are essential for email deliverability. Without these records, your emails risk being classified as spam by Gmail, Outlook, and other email providers.
• SEO and migration: during a site migration (server change, HTTPS transition, CDN setup), correct management of DNS records and TTLs is crucial to avoid any service interruption and SEO ranking loss.

How It Works

DNS resolution follows a multi-step process. When you type kern-it.be in your browser, it first checks its local cache. If the address is not cached, the request is sent to your Internet Service Provider's DNS resolver (or a public resolver like 1.1.1.1 or 8.8.8.8).

The resolver follows the DNS hierarchy: it queries a root server, which redirects it to the .be TLD (Top-Level Domain) server, which redirects it to the authoritative name server for the kern-it.be domain. This authoritative server returns the corresponding IP address, which the resolver caches (according to the TTL) and returns to the browser. The browser can then establish a TCP connection with the web server.

The main DNS record types are: A (server IPv4), AAAA (IPv6), CNAME (alias to another domain, used for CDNs), MX (mail servers), TXT (verification, SPF, DKIM), NS (authoritative name servers), and SOA (zone information). Each record has a TTL (Time to Live) that defines the cache duration, typically between 300 seconds (5 minutes) and 86,400 seconds (24 hours).

Concrete Example

When deploying a new Wagtail site for a Belgian client, KERN-IT systematically configures DNS records. The domain is managed through Cloudflare, which acts as both DNS provider and CDN. The A record points to the IP address of the Linux server hosting the Django/Nginx/Gunicorn application. A www CNAME record redirects the www subdomain to the main domain.

MX records are configured for the client's email service. TXT records include SPF (authorising legitimate mail servers), DKIM (cryptographic email signing), and DMARC (policy for handling unauthenticated emails). An additional TXT record enables Google Search Console verification for SEO monitoring. The TTL is set to 300 seconds during the migration phase (to allow rapid changes) then increased to 3,600 seconds in steady state.

Implementation

1. Choose a DNS provider: Cloudflare (free, fast, with integrated CDN), AWS Route 53 (reliable, integrated with AWS), or your domain registrar. Prefer a provider with an anycast network for fast resolution.
2. Configure basic records: create A (or AAAA) records pointing to your server, the www CNAME, and MX records for email.
3. Secure email: add SPF, DKIM, and DMARC records. Without these three records, your emails risk being rejected or classified as spam.
4. Configure TTL: use a short TTL (300 seconds) during migrations and changes, then increase to 3,600 seconds or more in normal operation to reduce DNS server load.
5. Enable DNSSEC: if your provider supports it, enable DNSSEC to cryptographically sign your DNS records and prevent DNS spoofing attacks.
6. Monitor resolution: use tools like dig, nslookup, or DNS monitoring services (Pingdom, UptimeRobot) to verify resolution works correctly and detect anomalies.

Associated Technologies and Tools

• Cloudflare: free DNS provider with integrated CDN, DDoS protection, and DNSSEC.
• AWS Route 53: highly available DNS service with latency-based and geolocation routing.
• Let's Encrypt: free SSL certificates, often managed via DNS challenges for validation.
• dig / nslookup: command-line tools for diagnosing DNS resolution.
• SPF / DKIM / DMARC: email security DNS records, essential for deliverability.

Conclusion

DNS is the invisible but indispensable infrastructure that makes the Internet navigable. Correct DNS configuration is the first step of any web deployment, and misconfiguration can make a site inaccessible or compromise email deliverability. At KERN-IT, we pay careful attention to DNS management for every project: choosing a reliable and fast provider, rigorous record configuration, securing with DNSSEC and email security records. For Belgian companies deploying Django or Wagtail sites, professional DNS management is a modest investment that prevents potentially costly problems.