A Brief Introduction of Domain Names:
What is a Domain Name? Before we can go into what a domain
name is I'm going to tell you why we need them as the answers
compliment each other. The Internet is just a really big
collection of connected computers (a network). For the purpose
of explaining domain names you can think of the Internet a bit
like the phone system and just like the phone system every
computer on the Internet has it's own phone number except an
Internet phone number is called an IP addresses. This address is
made up of up to 12 digits in the form 123.123.123.123,
computers use these IP addresses to send information to each
other over the Internet.
A domain name is an alias for an IP address. Now what is an
IP address? An IP address is a numeric code that signifies where
to look through the Internet for content. An example of an IP
address would be 22.226.141.25. Rather than typing in a long and
easily forgotten IP address, a domain name helps you by typing
an easily remembered name to access the same site.
When the Internet was first created it quickly became clear
that these IP addresses were not easy to remember and another
method was need to make these addresses more human friendly. The
solution to this was the Domain Name System (DNS). Basically the
DNS is a really really big phone book for computers. When you
type a web site address into your web browser it checks the DNS
for that website name and finds the IP address. Once it has the
IP address it can then send a message to that computer and ask
it for the web page you wanted.
Ok so you know a domain name is part of a web site address
but which part? Lets look at a website address so we can
identify and discuss what bit of it is a domain name.
http://www.ebiznewz.com/index.html
The above address is the home page of the eBusinessNews web
site. It can be split into 3 main parts. The first part is
http:// this just tells your web browser what kind of
information it is going to get and how to get it. The last part
is /index.html this is name of the files on the remote computer
that you want your browser to get. The bit in the middle
www.ebiznewz.com is a domain name. This is the
name that your computer sends to the DNS to get back the IP
address.
So you know what a domain name is and that there is a phone
book called the DNS to change your easy to remember domain name
into an IP address that you computer can understand. The
Internet phone book (DNS) is special in that everyone on the
Internet needs to be able to use it. This makes the DNS very
very big (100+ million addresses big). Due to the size of this
phone book it needed to have a carefully organised and managed
structure.
Domain name Servers (DNS) are an important but invisible part
of the internet, and form one of the largest databases on it.
Each machine on an internet is assigned a unique address, called
an IP address, which is 32 bit number and is expressed as 4
octets. The method user to represent these IP addresses is known
as dotted decimal Notation". A typical address looks like this:
199.249.150.4
It is very difficult to keep in mind the IP addresses of all
the websites we visit daily, because it's not easy to remember
strings of numbers. However, we do remember words. This is where
domain names come into the picture. If you want to connect to a
particular site, you need to know its IP address but do need to
know its URL. The DNS gets the mappings of the IP addresses and
the corresponding names.
DNS converts the machine names (such as www.xyz.com) to IP
addresses (such as 199.249.150.9). Basically, it translates from
a name to an address and from an address to a name.
The mapping from the IP address to the machine name is called
reverse mapping. When you type http://www.xyz.com into your
browser, the browser first needs to get the IP address of
www.xyz.com. The machine uses a directory service to look up IP
addresses and this service is called DNS. When you type
www.xyz.com your machines firsts contacts a DNS server, asking
it to find the IP address for www.xyz.com. This DNS server might
then contact other DNS servers on the internet. DNS is therefore
is considered as the global network of servers. The great
advantage of DNS is that no organization is responsible for
updating it.
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