Domain Name System: The telephone book of the internet

IP addresses consist of a seemingly confusing arrangement of numbers. In some cases (with IPv6 addresses), letters are also added to the mix. However, because people find it difficult to imagine what the mixture of numbers and letters means, and we don't remember them easily either, Paul Mockapetris developed the Domain Name System (DNS for short) in 1983 so that websites can be accessed via so-called domains.
You can also think of it as a large Telephone directory of the Internet of the Internet.
And without telling Google that a website exists, it will be difficult for Google users to find the website.

How does it work?
A domain name system is installed on a name server (NS for short) and can store various entries, including Resource records called resource records. The DNS servers are connected to each other and only manage individual domains. They then transmit entries to servers from a higher level. These servers contact other servers in the same way, which can also be addressed on the client side.
At first glance, this seems dauntingly complex and complicated. However, with the help of server hierarchies and the option of caching, it is a very reliable and durable system.

Wait a minute. Caching?
As soon as a domain is called up, an IP address is requested. This constant querying could lead to DNS server overload - this is where the caching option comes into play. The entries are simply stored for a certain period of time by the DNS servers and also the PCs. This is similar to the browser cache, except that it is the cache of the computer's operating system.

The most important DNS entries:

• A Resource Record:

This record assigns an IPv4 address to a DNS name. This resource record is the most common in the DNS.

• AAAA Resource Record:

Also called "quad-A". This has the task of assigning an IPv6 address to a DNS name.
AAAA and A are therefore the most important entries so that we do not have to enter the IP addresses.

• CNAME

Abbreviation for Caonical Name Record. It represents an Alias of the DNS name of a host and is used to set up a forwarding to another domain.
As an example of use: A CNAME record can contain the address www.beispiel.com to the actual page of the domain "example.com". Now you might think that the addresses would be identical anyway, but this is not the case. That is why it is important to have a CNAME entry so that you do not have "example.com" and end up on an error page.
Another example of the use of CNAME would be English and German language views of the website. A CNAME record is required so that these two are linked to the same website.

• TXT Resource Record

These are text entries that can contain SPF entries, for example. The SPF (=Sender Policy Framework) contains information on Spam protection and can also be linked to the MX record.

• MX Resource Record

This only refers to the E-mail Service and specifies the FQDN (Full Qualified Domain Name) under which the email server for a domain can be reached. This means that this resource record does not refer to IP addresses.

• SRV

Service Resource Record. It can be used to list and assign IP-based services in a domain. This allows the accessibility and availability of a domain's services to be determined using a DNS query. Further information is provided for each service, such as the server name that provides this service.