What is DNS (Domain Name System)?

DNS: definition and purpose

Computers find each other on the network through IP addresses such as 203.0.113.10 or, in the longer variant, IPv6. People, by contrast, remember names. The Domain Name System connects the two: it is a globally distributed, hierarchical directory that assigns the matching addresses and other details to domain names. It was developed in the 1980s and remains the backbone of internet use today.

Besides websites, DNS also controls where emails are delivered and whether services such as Microsoft 365 or Google Workspace are enabled for your domain. A wrong setting therefore often affects not just the website but a company’s entire email traffic.

How name resolution works

When someone enters example.com in a browser, the device first asks a resolver, usually the one run by the internet provider or a public DNS service. If it does not know the answer, it asks the root servers, the servers for the .com extension and finally the domain’s authoritative name servers, one after the other. The result is cached for a set period, the TTL (time to live).

The individual entries are called DNS records. They are maintained with the provider whose name servers are registered for the domain. Changes do not take effect everywhere at once, because caches at providers and on devices may keep serving the old values until the TTL expires. That is exactly why a move has to be prepared.

• A and AAAA: point the domain to an IPv4 or IPv6 address
• CNAME: redirects one name to another name
• MX: defines the mail server for incoming email
• TXT: holds verifications and email protection such as SPF, DKIM and DMARC
• NS: names the domain’s responsible name servers

Real-world example: moving a website without email downtime

A trades business moves its website to a new host. If it simply switches the domain’s name servers without carrying over the existing records, it unintentionally cuts off the MX entries. Customer emails are then lost even though the new website works perfectly.

A planned approach is better: document the existing records, lower the TTL a few days beforehand, create and test the records with the new provider, and only then switch over. That way, the change stays practically invisible to customers and staff.

Security, common mistakes and imple­menta­tion

DNS is a popular target for attacks, for example through forged responses or hijacked accounts at the provider. DNSSEC signs responses cryptographically so they cannot be altered unnoticed. SPF, DKIM and DMARC help against forged sender addresses. Access to domain management should be protected with two-factor authentication.

Nano Concepts reviews and documents your DNS configuration, plans moves so that your website and email stay reachable, and sets up sender authentication so your messages arrive reliably and nobody can forge emails in your name. If you wish, we also take care of the ongoing maintenance of the records.

• Switching name servers without carrying over the MX and TXT records
• Forgotten subdomains that point to services no longer in use
• TTL values that are too high right before a move
• Missing SPF, DKIM and DMARC records that send emails to the spam folder