A General Overview of DNS

What is DNS?

Domain Name Servers, or DNS, is the internet's guide to finding and connecting one source with another.  DNS is the computer directory that turns human identifiable names (domain names like yourdomain.com) into Internet Protocol (IP) addresses necessary (a series of numbers separated by periods) to be read by computers.

When you enter a Uniform Resource Locator (URL) into the search bar, i.e., www.example.com, it's transformed into an IP address like 193.135.34.20.  You don't see this happening, but this computer-understood translation directs your internet connection to the appropriate site.

Several root servers worldwide help your Internet Service Provider point to the appropriate name servers for your domain name. This allows your website visitors to visit your domain name without memorizing the IP address associated with your web hosting account by just typing in your domain name and is very similar to using a phone book to find someone's phone number.

Basic Terminology

Top-Level Domain (TLD)

The top-level domain is the suffix portion of the domain behind the dot.  For example, .com, .net, .org, .gov and .edu.  These TLDs are managed by various groups, decided upon by the Internet Corporations for Assigned Names and Numbers (ICANN), and distribute through registrars.

Hosts

The domain owner determines the host by assigning the computer or server to access the domain.  Domains take on many forms, but the most common are example.com (bare) and www.example.com (host definition).  As long as the names are unique, the hosts can be arbitrary.

Subdomain

A subdomain is the wording prefix that comes before the main domain. For example, subdomain.mydomain.com. Subdomains can be used to section off certain parts of a website and have their own setup. For example, you could have your main website on mydomain.com, and on subdomain.mydomain.com, you could have a WordPress site set up for a blog.

Fully Qualified Domain Name (FQDN)

A fully qualified domain name may include three parts: a host (www, for example), the domain name, and your TLD. A fully qualified domain name could be www.yourdomain.com or just yourdomain.com.

Name Server

A name server makes it possible to visit a website by going to the domain name instead of an IP address. All websites on the internet technically reside on an IP address, a series of numbers. Thankfully, we don't have to try to remember all those numbers, though, because name servers direct you to the correct place when you visit a domain name.

Zone File

A zone file represents the DNS zone where a domain resides. DNS zones are specific areas that are sectioned off within the domain name system (DNS). The zone file is a text file in the BIND format that provides records for that domain zone. It can be handy for many things. For example, you can use it to make backing up domain records easier or to fully migrate your zone to another server.

Records

DNS records provide the correct IP address for a website to the DNS server, then that information is sent to the hosting company so a website can be displayed. Common DNS record types include:

• A - maps a domain name to an IPv4 address.
• AAAA - maps a domain name to an IPv6 address.
• MX - used to deliver email for a domain (points to a mail server name, not an IP address).
• CNAME - used to map any aliases or other desired names to the true domain name (or subdomain).
• SRV - allows services like instant messaging and VoIP to be directed to an appropriate host and port.
• TXT - contains information for email and site validation, ownership verification, encryption, framework policies, etc.
• SOA - contains domain-related information used to direct how a DNS zone propagates to secondary name servers.
• NAPTR - maps servers and addresses used with the session initiation protocol (SIP) or internet telephony systems.