A domain name is simply a textual address by which anyone can find your host machine on the Internet.

A domain name always contains a few components, i.e. labels, which are separated by a dot (period), thus: www.abc.com.my 

The structure of a domain name conforms to the DNS Internet naming hierarchy which follows a tree structure. This structure allows computers to find each other on the Internet (see How are domain names translated into IP addresses?).

At the very top of this hierarchy is the root (which does not appear in the domain name). The next level down of this hierarchy is the top level domain (TLD), the one after that being the second-level domain, and so on. 

The TLD is what appears at the far right end of a domain name. In the example above, the TLD is .my. TLDs come either as country codes domain names like .uk, and .jp, or generic top-level domain names like .com, .net, or .gov.

URL stands for Uniform Resource Locator, a form of address that specifies the location of an object, usually a webpage or a website on the Internet. Here are some examples of URLs:

• http://www.abc.com.my/welcome.html
• http://abc.com.my
• http://abc.com/welcome/index.htm
• ftp://ftp.abc.com.my/something.gz
• mailto:someone@abc.com.my

A URL contains three parts, i.e.

• protocol (e.g. http, ftp, news, mailto)
• domain name of any Internet host (e.g. www.abc.com.my, abc.com, abc.com.my)
• path or file name (e.g. welcome.html, welcome/index.html, something.gz)

Therefore, a domain name is used in a URL.  When you use the web or send an e-mail message, a domain name is used.  For example,

• the URL http://www.abc.com.my contains the domain name abc.com.my
• the e-mail address somebody@abc.com.my contains the domain name abc.com.my

They are different forms of Internet addresses.

An IP address or network address is a numeric form of address that identifies every machine on the Internet. Therefore, every machine has a unique IP address. For example, the IP address of the abc company website could be 192.228.180.200.

A domain name is a textual form of address that is easier for humans to remember than the string of numbers that makes up an IP address. For example, the domain name of that same abc company could be http://www.abc.com.my. However, this domain name could have more than one IP address.

When you browse a particular web site, it is actually the IP address that determines the successful communication between your computer and the website. IP addresses could be said to be computer-friendly, while domain names are human user-friendly.

The technology that allows this to happen is called Domain Name System (DNS) technology. This provides the mapping between user-friendly domain names and computer-friendly numeric IP addresses. DNS is an Internet protocol and distributed database.

Here’s how DNS technology works. DNS comprises three components: the name server, the resolver, and the domain.

• The name server is also known as the DNS server. It stores domain name information or gets domain name information from other name servers and stores them temporarily in caches to eliminate unnecessary network traffic.
• The resolver is a DNS client that queries the name server to resolve an Internet hostname.
• The domain is the DNS content which is held in a hierarchical tree structure for translation of names to network addresses and mail routing.

The hierarchical tree structure has these functions:

• Gives rough indication of the type of organisation and its location e.g. names that end with .my, are related to Malaysia
• Allows automatic navigation in the system through the DNS tree
• Allows delegation of responsibility for a branch in the tree to multiple parties

Take for example, the domain name www.abc.com.my. The Internet naming hierarchy for this domain is:

 
     .(root)
     |
     my
     |
    com
     | 
    abc
     |
    www

At the top of the DNS database tree are what are called root name servers. Each root name server knows the IP addresses of the name servers handling the top level domain names. In our example, the top level domain name is .my. If a querying name server would like to find out the IP address of www.abc.com.my:

• First, it would ask a root name server for the IP addresses of the .my domain name servers. The root name server returns the IP addresses of the .my domain name servers to the querying name server.
• Then, the querying name server asks a .my domain name server for the IP addresses of com.my domain name servers. The .my domain name server returns the IP addresses of the com.my domain name servers to the querying name server.
• Then, the querying name server asks a com.my domain name server to find out the IP addresses of abc.com.my domain name servers and obtains the information needed.
• Finally, it queries the abc.com.my domain name server. Each abc.com.my domain name server has detailed address information for the hosts in that domain. This most specific name server supplies the querying name server with the IP address of the host machine called www.abc.com.my.

The process is graphically presented below:

Example Query: What is the numeric address (IP address) of a machine with the hostname www.abc.com.my?
Example Response: 192.228.180.200
 
 

                         . (root) name server
                        ^
                       /
                      v    
remote name server                 <---->  .my name server
- sends query to other name server
- gives response to client    
                                   <---->  .com.my name server
                 ^        ^                            
                 |         \    
                 |          v
                 |            abc.com.my name server 
                 v
remote DNS client (resolver)
- sends query to name server

Every domain name has name servers that handle queries for its information or records. What’s in a name server? It contains one or more DNS databases to store Internet hostnames and their associated IP addresses. DNS records need to be maintained by people.

Name servers are queried by various programs and other name servers to convert domain names into IP addresses all day long. Each name server, called a primary name server, usually has a back-up server, called a secondary name server, so that this can be done uninterrupted. Both primary and secondary name servers hold the authoritative data of a domain name.

If you wish to receive e-mail from the Internet you need to have a Mail Exchange (MX) record for your domain name in your DNS database. There are two ways to get name servers for your domain name:

• create and administer them yourself
• pay an Internet Service Provider or a hosting company to handle them for you

• It contains the information of that domain name
• Maintenance of the DNS records of a domain name is done at the primary name server level
• If you choose to administer the primary name server yourself, you can make changes, additions and deletions at your own convenience

• It contains the exact copy of the domain name information as the primary name server, which is downloaded from the primary name server periodically
• It acts as the alternative server if the primary name server goes down
• If you choose to administer a secondary name server only, you do not have to worry about the maintenance of a particular domain name