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8.30.13 Domain Name Resolution (DNR)

You already know that communication between computers on a network takes place with the help
of IP addresses. However, to access a particular website, you use its URL because it is much easier
to remember than the IP address. When you use the URL to access a website, your computer needs
to find its matching IP address. How does it find this address? The answer is: by using the Domain
Name Resolution (DNR). DNR is the name given to the process by which your computer finds the
IP addresses of domain names.
The DNR process takes place in the background, and can be explained in the following steps:

1. Enter the domain name of the website that you want to access in the Web browser.
2. The Web browser issues a command to the operating system of your computer to generate the
IP address of the given domain name.

The domain name is resolved according to the configuration of the operating system you are using.
Different operating systems, such as Windows, XP, Windows 7, Linux, and Unix have different
configurations.
This is done in the following manner:
 Generally, the operating system maintains a HOSTS file, which contains a list of the IP addresses
of some domain names. Therefore, the operating system first checks this file to find the IP
address of the given domain name.

 If the IP address is not found in the HOSTS file, the operating system connects to the DNS server
on a network. The DNS server maintains a directory containing a list of all the domain names
and IP addresses that are registered on the internet. The DNS server finds the IP address of the
given domain name and returns it to the operating system.
3. After obtaining the IP address, the operating system sends it to the Web browser that has
requested it.

CTM: A web browser is a WWW client that navigates through the WWW and displays web pages.

8.30.14 Web Scripting

Website Scripting is used for creating web pages to publish them on the web interactively. The
communication between web browser and web server happens through small programs called
web scripts. Script is a programming language which, when executed, displays the web page. The
written codes for a script may be used by the server side or may be used by the client side as per
the requirement. The tasks which are executed by a web server are interpreted and automated
through the web scripts written in Web Scripting Language.

CTM: A script is a list of commands embedded in a web page which are executed by a certain program or
scripting engine.

(a) Client-Side Web Scripting Languages

Client-side scripting enables the user to interact with web pages. The client-side scripts are
downloaded at the client end and then interpreted and executed by the web browser. The
client-side scripting is browser dependent and, therefore, the browser must be scripting- Computer Networks
enabled that can interpret the script code. Examples of client-side scripting where it is used are
online games, downloading data from the server, etc.
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