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.
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
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