A2 ICT

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A2 ICT
Module 5
14.4 Communication and Information Systems
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
The journey begins in a browser, where a URL is
typed into the address bar.
In this example, the journey is to the KHS Online
website.
http//www.kesgrave.suffolk.sch.uk/
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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).
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
After typing the URL the browser sends an
instruction to the computers modem to dial the
users ISP.
This is called Dial-Up Networking (or DUN).
The modem converts the digital signal to analogue
for communication down the telephone line (PSTN)
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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!
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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 browsers address bar
to the ISP server.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
Domain Names and IP Addresses
Fully Qualified Domain Names (FQDNs) - such as
www.kesgrave.suffolk.sch.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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.kesgrave.suffolk.sch.uk/Curric/ICT/inde
x.html
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
How a Domain Name is structured
http//www.kesgrave.suffolk.sch.uk/Curric/ICT/inde
x.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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
How a Domain Name is structured
This part is the FQDN (Domain Name). Also known
as the Root Domain.
http//www.kesgrave.suffolk.sch.uk/Curric/ICT/inde
x.html
The .uk part of the root domain is a TOP LEVEL
DOMAIN. There are many of these, including .com
and .edu. New ones have just been introduced,
including .biz and .info.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
How a Domain Name is structured
http//www.kesgrave.suffolk.sch.uk/Curric/ICT/inde
x.html
These specify the folder names on the web server.
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.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
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.kesgrave.suffolk.sch.uk/Curric/ICT/inde
x.html
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
Conversion to an IP Address
http//www.kesgrave.suffolk.sch.uk/Curric/ICT/inde
x.html
http//212.44.57.62, etc.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
The request is made to the server at
Schoolmaster.net to send a copy of the first page
of the KHS Online website to ISP server.
It transfers the web page via HTTP Hypertext
Transfer Protocol.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
The ISP then transfers the web page to the
requesting browser, again by HTTP and TCP/IP.
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14.4 - Communication and Information Systems
WWW Infrastructure
Journey through the Internet
The browsers parsing engine interprets the web
page code and displays the web page.
The journey is now complete, and has only taken a
few seconds.