DNS - papersocean

Computer Networks:

Physical Layers

Data link Layer(DLL)

Network Layer

Transport Layer:

Session and Presentation Layer:

Application Layer:

Domain Name Service (DNS)

The Domain Name Service DNS:
Instead of using the full 32 bit IP address many system adopt meaningful names for their device and network. Network names usually reflect the organization name such as www.bitstudies.com festivalcelebrate.com.

Translation between this names and the IP address would be practically Impossible on an internet wide scale.To solve the problem of network names : the network information centre NIC maintain a list of network names and the corresponding network Gateway addresses.

This system grew from a simple flat file list (which was search for matches) to a more Complex system called the domain name service DNS. When the network become too numerous for the flat file system to function efficiently. DNS use hierarchical architecture much like the Unix file system.
The first level DNS is to divide network into categories of sub network such as .com for commercial institution, mil for military, edu for education and so on. This is called domain name the organization system management and further divide the companies sub network as Desire with each network called a sub domain

For example the system www.bitstudies.computernetwork.com

7 first level domain name has been established by the NIC so far these are as follows:

.arpa An ARPANRET internet identification;
.com commercial institutions.
.gov Any government body
.mil military
.net network used by internet service provider
.org that does not fall into one of the Other category.

How DNS works:

Consider and example suppose that a user sitting at a computer in india needs to communicate with computer “system 1″ located at company bitstudies in USA. the user must specify the Computer’s name

For example the full name might be studies.com.

Before an application program running in India can communicate with computer “system 1”. It needs to obtain computer “system1’s ” IP address. To find the address the application used the internet domain name system.

Does an application program in India need to know the address of the domain server for company bitstudies?

No, the domain name system is completely automatic. A computers on the internet only needs to know the location of one domain name server usually a local one the domain name server handers the look up automatically.

Is the figure show finding the IP address for a remote name take four steps:

Step 1:

an application local domain name server in India. The application is ask the server what is the IP address of the computer name system one at company bitstudies.?

Step 2:
The domain name server in India contact the domains server at company bitstudies.

Step 3:
The server at company bitstudies responded by sending and answer

Step 4:

The local domain name server in India send answer back to the original application program.

Note that the domain service perform all four steps without contacting computer system 1 similar to the way directory assistant can provide someone’s telephone number without calling that person.