The document describes the journey a request takes from a web browser through the internet to a web server and back. It begins with the user entering a URL in their browser. Their computer then connects to their Internet Service Provider who directs the request to the appropriate DNS server to convert the URL to an IP address. The IP address is used to retrieve the requested page from the web server, which is then sent back to the user's browser to be displayed.

2. WWW
Journey through the Internet
Infrastructure
The journey begins in a
browser, where a URL is
typed into the address
bar.
In this example, the
journey is to the RA
Online website.
http://www.rothesayacademy.org.uk/

3. WWW
Journey through the Internet
Infrastructure
A browser is a piece of
software which interprets
HTML and other scripting
languages to produce a
web page.
A URL is a Uniform Resource
Locator (a “web address”).

4. WWW
Journey through the Internet
Infrastructure
After typing the URL the
browser sends an instruction
to the computer’s modem
to dial the user’s ISP.
This is called Dial-Up
Networking (or DUN).
The modem converts the
digital signal to analogue for
communication down the
telephone line (PSTN)

5. WWW
Journey through the Internet
Infrastructure
An ISP is an Internet Service
Provider – a company which
specialises in providing
Internet access. In this
example, the modem is
dialling Virgin Net.
A modem is not the only
way of getting on the
Internet – ISDN, DSL, Satellite
and many other services are
available and much faster!

6. WWW
Journey through the Internet
Infrastructure
In order for the computer to
be able to connect and
communicate with the ISP
server, the computer that is
dialling must have the
TCP/IP Protocols installed.

7. WWW
Journey through the Internet
Infrastructure
TCP/IP stands for Transport
Control Protocol / Internet
Protocol. You can see
whether this is installed on
your machine by looking in
the ‘Networks’ section of the
‘Control Panel’.

8. WWW
Journey through the Internet
Infrastructure
When the computer
connects to the ISP server, it
sends username and
password information via
TCP/IP to verify that this is a
legitimate connection.
The server tells the computer
what it is doing and this is
shown in the connection
window.

9. WWW
Journey through the Internet
Infrastructure
If the server recognises the
username and password
from its database, it agrees
to the connection.
The computer then sends
the URL that was originally
typed into the browser’s
address bar to the ISP server.

10. WWW
Journey through the Internet
Infrastructure
The URL is sent to the DNS at
the ISP. The DNS is the
Domain Name Server. This
converts the URL into an IP
Address which is then sent
to the ISP where the domain
is hosted for collection, via
the Internet Backbone.

11. WWW
Journey through the Internet
Infrastructure
The Internet backbone is
maintained by a NSP
(Network Service Provider).
When you dial-up, you do
not connect to the
backbone: your ISP does this
for you.

12. WWW
Journey through the Internet
Infrastructure
Domain Names and IP Addresses:
Fully Qualified Domain Names (FQDNs) - such as
www.rothesayacademy.org.uk are used to help Internet users.
This is because the Internet uses IP Addresses, not domain
names to find web sites and IP Addresses are strings of
numbers, which are difficult to understand.
The DNS (Domain Name Server) knows the IP Addresses of all
registered web sites. It converts the domain names into IP
Addresses and uses this to request a web page from that IP
Address.

13. WWW
Journey through the Internet
Infrastructure
How a Domain Name is structured:
This specifies the PROTOCOL that should be used to fetch the
information. HTTP is ‘Hypertext Transfer Protocol’ which means
‘rules for moving web pages from one computer to another’.
http://www.rothesayacademy.org.uk/Curric/ICT/index.html

14. WWW
Journey through the Internet
Infrastructure
How a Domain Name is structured:
http://www.rothesayacademy.org.uk/Curric/ICT/index.html
WWW stands for ‘World Wide Web’. This part of a domain
name instructs the ISP to look on this part of the Internet for
the information. It also forms part of the web server name.

15. WWW
Journey through the Internet
Infrastructure
How a Domain Name is structured:
This part is the FQDN (Domain Name). Also known as the Root
Domain.
http://www.rothesayacademy.org.uk/Curric/ICT/index.html
The ‘.uk’ part of the root domain is a TOP LEVEL DOMAIN.
There are many of these, including .com and .edu.

16. WWW
Journey through the Internet
Infrastructure
How a Domain Name is structured:
http://www.rothesayacademy.org.uk/Curric/ICT/index.html
These specify the folder names on the web server. Called the path. In this
instance, the folder for the ICT Online website is inside the ‘Curric’ folder. It
is important to remember that web addresses are CASE SENSITIVE.

17. WWW
Journey through the Internet
Infrastructure
How a Domain Name is structured:
The final part of the web address specifies the name of the web page.
These will normally end in ‘.html’ or ‘.htm’.
http://www.rothesayacademy.org.uk/Curric/ICT/index.html

18. WWW
Journey through the Internet
Infrastructure
Conversion to an IP Address:
http://www.rothesayacademy.org.uk/Curric/ICT/index.html
http://212.44.57.62, etc.

19. WWW
Journey through the Internet
Infrastructure
The request is made to the
server at argyll-bute.sch.uk
to send a copy of the first
page of the RA Online
website to ISP server.
It transfers the web page via
HTTP – Hypertext Transfer
Protocol.

20. WWW
Journey through the Internet
Infrastructure
The ISP then transfers the
web page to the requesting
browser, again by HTTP and
TCP/IP.

21. WWW
Journey through the Internet
Infrastructure
The browser interprets the
web page code and
displays the web page.
The journey is now
complete, and has only
taken a few seconds.