Internet
This is the world-wide network of computers accessible to
anyone who knows their Internet Protocol (IP) address
- the IP address is a unique set of numbers (such as 209.33.27.100)
that defines the computer's location. Most will have accessed a computer
using a name such as http://www.hcidata.com.
Before this named computer can be accessed, the name needs
to be resolved (translated) into an IP address. To do this your browser
(for example Netscape or Internet Explorer) will access a Domain Name
Server (DNS) computer to lookup the name and return
an IP address - or issue an error message to indicate that the name
was not found. Once your browser has the IP address it can access
the remote computer. The actual server (the computer that serves up
the web pages) does not reside behind a firewall - if it did, it would
be an Extranet. It may implement security at a directory level so
that access is via a username and password, but otherwise all the
information is accessible. To see typical security have a look
at a sample secure directory - the username is Dr and
the password is Who (both username and password are case
sensitive). |
Intranet
This is a network that is not available to the world outside of the
Intranet. If the Intranet network is connected to the Internet, the
Intranet will reside behind a firewall and, if it allows access from
the Internet, will be an Extranet. The firewall helps to control access
between the Intranet and Internet to permit access to the Intranet
only to people who are members of the same company or organisation.
In its simplest form, an Intranet can be set up on a networked PC
without any PC on the network having access via the Intranet network
to the Internet.
For example, consider an office with a few PCs and a few printers
all networked together. The network would not be connected to the
outside world. On one of the drives of one of the PCs there would
be a directory of web pages that comprise the Intranet. Other PCs
on the network could access this Intranet by pointing their browser
(Netscape or Internet Explorer) to this directory - for example
U:\inet\index.htm.
From then onwards they would navigate around the Intranet in the same
way as they would get around the Internet. |
Extranet
An Extranet is actually an Intranet that is partially accessible to
authorised outsiders. The actual server (the computer that serves
up the web pages) will reside behind a firewall. The firewall helps
to control access between the Intranet and Internet permitting access
to the Intranet only to people who are suitably authorised. The level
of access can be set to different levels for individuals or groups
of outside users. The access can be based on a username and password
or an IP address (a unique set of numbers such as 209.33.27.100 that
defines the computer that the user is on). |
