The Role of Fully Qualified Domain Names on the Internet

While most people are aware of the importance of a domain name to access a particular web site, most people are unaware of just how important a fully qualified domain name is or why having one helps enable the internet to function as we know it.

The Birth of Fully Qualified Domain Names

In the mid to late 1980's when the internet was still in its infancy there
were several protocols put into place by the IETF that would provide
uniformity to the internet as it grew. These protocols have allowed the
internet to be scaleable and grow at the phenomenonally rapid rate it has.
One of the most important of these protocols was the establishment and
implementation of the domain name system.

The domain name system provides a way for every entity that is connected
to the Internet such as a computer, web server and any other resource to
have its own unique identification and place in the Internet framework. At
its core these identifications are all numeric not character based. Domain
names as most people think of them were brought into existence in order to
make it easier on people to remember and keep track of. One key element
of the Domain Name System is to translate domain name into the required
numeric identities.

While the domain name system is hierarchial in nature if it were put into
illustrative form it would look very similar to a diagram of a family
tree. Much like you have a specific place on your own family tree every
fully qualified domain name has its own particular place in the domain
name system hierarchy as well.

Fully Qualified Domain Names

A fully qualified domain name specifies exactly where it is in the domain
hierarchy. It is complete and total in nature. No other domain name can
have its exact same location. Much like there is only one 'you' and you
can only be in one place, there is only one fully qualified domain name
for every domain level and it can only be in one place also.

Every domain name in the domain name system contains certain information
for every domain level. While that information appears in the same place
in the system for every domain name, the location of each of the domain
names are all different which makes the fully qualified domain name
different as well.

Format of Fully Qualified Domain Names

The format of a fully qualified domain name is always the same. This helps
the domain name system determine where the domain name is within the
hierarchy.

The three requirements needed for a fully qualified domain name are the
zone file, top level domain and root zone.

For example, the fully qualified domain name for gmail's pop mail is

pop.gmail.com.

Take note of the dot on the end. That is not a typo. All fully qualified
domain names have what is known as a trailing dot on the end. This goes
to what seems to be an empty label but is in fact an unnamed DNS root
zone.

To put this into human terms, let's revisit the family tree example from
above. You know that every person on your family tree is a human being so
it isn't necessary to put human being after every person's name.

This is the same for fully qualified domain names.

The DNS root zone is the root zone for what most people refer to as the
Internet. As such there isn't any reason to write out "Internet" at the
end of every domain name. Every domain name in the Domain Name System has
the same root zone so it isn't necessary to write it out each time.

So what about the trailing dot?

If a trailing dot makes a fully qualified domain name 'official' why don't
we see it used more often?

The reason is simple. Ease of use. In most cases the systems which
require fully qualified domain names have been set up so that the trailing
dot isn't required. Instead, the trailing dot is implied even if it isn't
written out.

For example, we don't need to enter a trailing dot after we enter a domain
name into a web browser although in most major browsers we can add it if
we want to. The DNS system does that automatically for us. It knows where
to go to find information about the domain name we want to access without
us having to type the period at the end.