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Networking
Basics:
TCP/IP Basics
TCP/IP Introduction
The TCP/IP protocol is the
protocol that holds the Internet together. It is also
found in most internal company networks.
You might ask yourself, why
should I learn about another protocol? The answer is
simple, as the internet becomes more popular and more
applications are developed with a bias towards the Internet
and TCP/IP, you will be forced to understand
how this protocol works and maybe eventually install
it on your own network.
How does it work?
Each person is given (either
automatically or manually) his or her own IP address.
This IP address is unique to them and can not be used
by anyone else inside your network. Think of an IP address
as a telephone number, if several people had the same
telephone number in your town, then there would be a
conflict.
A typical IP address might look something
like this:
220.0.0.80
That's it, it's not a huge number
that takes half an hour to type in, it's a simple four
digit number that identifies your PC.
You can't just make up these
addresses, there is a numbering convention that you
must use. Below is an example of how TCP/IP addressing
works.
Different IP address classes
There are different classes
of IP address. The three most commonly talked about
are Class A, Class B and Class C IP addresses. The IP
address in the above example (220.0.0.x) is known as
a Class C IP address.
| Class |
Network
ID |
Host
ID |
Example |
| A |
1-126 |
x.x.x |
1-126.x.x.x |
| B |
128-191.f |
x.x |
128-191.f.x.x |
| C |
192-223.f.f |
X |
192-223.f.f.x |
(f) means fixed address that can not change.
(x) means a value between 0 and 255
Subnet Masks
Your computer has
no way of knowing what kind of IP address you have,
this means that there has to be some way of letting
your software extract the network ID from the IP address.
To do this, you can use subnet masks. Typically a subnet
mask will look like this: 255.255.255.0. This tells
us quickly that we are using a Class C IP address as
the first three 255's tell us that these individual
numbers can not change. The zero tells us that this
is the only digit that we can use, so it has to be a
Class C IP address.
If we had an IP address of 128.10.11.23
and a subnet mask of 255.255.0.0 then we can quickly
see that we have a Class B IP address.
The whole point of a subnet mask is
to tell the computer which is the Network ID and which
is the host ID.
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