Welcome back, guys.
So now let us have some discussion regarding website's domain name.
That is, if you want to launch your own website, then what should be the name of a website?
In other words, what should be the domain name of your website?
So remember, the naming of a website is just not random, but it has to be consistent with the DNS
tree.
So a website name and a name of the website is also called as domain name.
So a website name also called domain name is just not any random sequence of words or strings.
A website name needs to be constructed systematically, keeping DNS hierarchy in mind.
Right?
So a website name is constructed of individual words called literals.
These literals are actually the name of DNS servers in the path of DNS tree, starting from the root
DNS server towards the leaf of DNS tree.
Right.
So for example, suppose there is a website name called customer support dot Microsoft.com.
So how many literals it has, It has four literals that is customer is one.
Literal support is one literal Microsoft and com.
So the name of this website is composed of four literals.
Right?
So now let us see how website domain name is constructed or derived from DNS system with the help of
an example.
So remember, you just cannot choose any random sequence of words or literals as a name of your website,
right?
So whatever name you choose to be, the name of your website has to be consistent with the DNS tree.
So now let us take an example.
So you can see in this diagram I have shown you the root DNS server and the top level DNS servers,
right and below the top level DNS server called com, there is a Microsoft DNS server.
And as a child of this Microsoft DNS server, we have another subdomain DNS server called support.
So this is the DNS tree and we have been discussing about this DNS tree quite a bit.
Now.
So a website name is nothing, but it is a sequence of DNS servers in the DNS tree but in the opposite
order.
So let us take an example.
Suppose you have a website called w w w dot customer support dot Microsoft.com Right now, given this
name of a website, how does the name of this website is dependent on this DNS tree?
Let us try to understand that.
So for a given website, always assume that there is a dot which is appended at the end of this website
name.
This dot actually represents the root DNS server.
So as soon as you type out the name of your website in a browser, your browser automatically adds a
dot in the end of your website name.
So this dot represent a root DNS server.
Then the first literal from the last is com.
So clearly here the.com represents the top level DNS server that is this one.
Then the second literal from the last is the Microsoft.
So again, Dot Microsoft is the DNS server of Microsoft Corporation.
Right.
And again, the third literal is the support.
So support is nothing, but it is a Microsoft sub domain DNS server.
Right.
And the final literal is customer.
So customer is nothing, but it is the name of a server which actually provides a world wide web service
to the end user.
Right.
So this customer is not a DNS, but it is an actual server which provides the service.
So you can see that the name of the website is actually a composition of sequence of names of DNS servers
in the opposite order of DNS three.
That is starting from the root DNS server and moving towards the leaf of the DNS server.
So this is the root of the DNS server.
Then second is the com, then third one is the Microsoft and the fourth one is support.
And finally fifth one is the actual web server, which is providing world wide web service.
So you can see that the name of the website is the composition of names of DNS servers starting from
the root of the tree and moving towards the leaf of the DNS tree.
So this is how the name of the websites are derived.
Right now.
Let us discuss what exactly fully qualified domain name is.
So for a given website name, the fully qualified domain name is nothing, but it is a concatenation
of the name of a server which actually provides a service.
In this case, that server is customer server.
Right?
And the second part of fully qualified domain name is the name of is the domain name, which is actually
the composition of DNS servers starting from the root of the DNS tree up to the leaf of the DNS tree.
So the second part is actually called a domain name, where its first part is actually called a host
name.
So the host name, combined together with the domain name of a website is called Fully qualified domain
Name.
So what exactly fully qualified domain name represents?
What is the significance?
The significance is that that the fully qualified domain name uniquely identifies a server which provides
a world wide Web service.
For example, if I tell you that customer support dot Microsoft.com, what is that with this name?
With the help of a DNS system, you can uniquely identify that this name corresponds to this server.
So fully qualified domain name is actually the name of a server which actually provides a service and
given a fully qualified domain name, we can identify service providing server uniquely in the entire
world.
So you can say that fully qualified domain name is like a unique identity of the server which is providing
a service.
So remember, fully qualified domain name is the concatenation of name of a server which is providing
a service.
That name is called hostname.
And the second part of fully qualified domain name is the sequence of name of DNS servers starting from
the root of the DNS tree and going or moving towards the leaf of the DNS tree.
Right?
So fully qualified domain name is the concatenation of host name plus domain name.
So thus now concluding on fully qualified domain name.
Fully qualified domain name is nothing, but it is a unique identity of some physical server.
So in this case, the fully qualified domain name customer support dot Microsoft.com uniquely identify
this physical server which is running somewhere in the network.
So always remember that next time when you type out the website name in your browser, then think of
it like you are trying to access a physical server deployed somewhere in the network.
So your website name is nothing, but it is a name of the physical server.
And from that physical server you are actually trying to revoke the world wide web services.
So henceforth in this module, whenever I say domain name, it means that I am trying to refer to some
physical server which is running somewhere in the network.