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Domains and DNS

What a domain name is, how DNS turns it into the address of your server, and how nameservers, zones and records fit together.

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A domain is a name such as example.com that people type to reach your website or to send you mail. Computers find each other by numeric IP addresses, such as 203.0.113.10, and the Domain Name System (DNS) is the directory that turns a name into an address.

Registering a domain

Section titled Registering a domain

Each ending, such as .com, is run by a registry. You register a domain through a registrar, and the domain stays yours for the period you pay for. Coritan registers domains for 1–10 years at a time, and renews them for you while auto-renew is on (How domain registration works).

The registry also keeps a list of the nameservers for each domain: the servers that answer DNS questions about it. You choose them at the registrar.

How a name becomes an address

Section titled How a name becomes an address

When someone opens www.example.com, their device asks a resolver, a DNS server that their internet provider or network usually runs. The resolver asks the registry which nameservers answer for example.com, asks one of them for the address of www.example.com, and passes the answer back. The browser then connects to that address.

The resolver keeps the answer, so the next person who asks it gets the answer at once. The answer's TTL (time to live) says how many seconds the resolver may keep it.

Zones and records

Section titled Zones and records

The nameservers answer from the domain's zone: its list of records. Each record has a name, a type, a value and a TTL. These are the types you meet first:

Type What it says Example
A The IPv4 address of a name www points to 203.0.113.10
AAAA The IPv6 address of a name www points to 2001:db8::10
CNAME A name is another name shop points to shops.example.net
MX The servers that take the domain's mail @ points to mx1.mail-fra.coritan.com
TXT Text that other services read, such as the list of servers allowed to send your mail @ holds v=spf1 include:_spf.mail-fra.coritan.com -all

A name in a zone is written relative to the domain: www means www.example.com, and @ means example.com itself. A name under your domain, such as shop.example.com, is a subdomain, and you create one by adding a record for it. DNS record types lists every type Coritan hosts.

Why a change takes time to reach everyone

Section titled Why a change takes time to reach everyone

Coritan's nameservers serve a change as soon as you save it. A resolver that already holds the old answer keeps it until its TTL runs out, so some visitors see the change later than others. Before a planned move, lower the record's TTL a while ahead, so that the old answer expires sooner. A TTL can be from 60 seconds to one day (TTL).

Nameservers work the same way. After you change a domain's nameservers, resolvers keep asking the old ones until their cached answer expires (Change a domain's nameservers).

DNS at Coritan

Section titled DNS at Coritan
  • A domain you register on the Websites page starts on Coritan's nameservers, ns1.coritan.com to ns8.coritan.com, with a zone on your account (Register a domain).
  • For a domain registered somewhere else, add it to your account, then set its nameservers to Coritan's at its registrar (Add a domain you already own).
  • You edit a zone's records on the domain's DNS tab. Coritan signs each zone with DNSSEC from the moment you add it, which lets resolvers check that an answer came from the zone unchanged. You can switch signing off on the domain's Settings tab (Set up DNSSEC).
  • An A or AAAA record can be proxied. Coritan then answers with the addresses of its edge, which serves the site over HTTPS and checks each request before it reaches your server (Web proxies, origins and the WAF).

Next steps

Section titled Next steps