Page 12 - DCAP202_Fundamentals of Web Programming

Unit 1: Internet Basic

Unlike a phone book, the DNS can be quickly updated, allowing a service's location on the Notes
network to change without affecting the end users, who continue to use the same host name.
Users take advantage of this when they use meaningful Uniform Resource Locators (URLs) and
e-mail addresses without having to know how the computer actually locates the services.

Real Life Example

A lot of what has been discussed may be a bit confusing, so lets do a real life example. In the
flowchart below labeled Figure 1.2, you will see a computer trying to connect to www.google.com
and the steps it takes.
Figure 1.2: Computer Trying to Connect to www.google.com

We will discuss these steps below:
1. A User opens a web browser and tries to connect to www.google.com. The operating
system not knowing the IP Address for www.google.com, asks the ISP's DNS Server for
this information.
2. The ISP's DNS Server does not know this information, so it connects to a Root Server to
find out what name server, running somewhere in the world, know the information about
google.com.

3. The Root Server tells the ISP's DNS Server to contact a particular name server that knows
the information about google.com.
4. The ISP's DNS Server connects to Google's DNS server and asks for the IP Address for
www.google.com.
5. Google's DNS Server responds to the ISP's DNS server with the appropriate IP Address.

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