Networking

What is a network?

A network is a group of connected and communicating devices such as a laptop and a desktop or a computer and a printer or an iPhone and a Mac. So, it's basically any two or more devices talking with each other.

After defining a network we now to one of the most common word of today's world. It's INTERNET! Now there is a difference between the word Internet and internet. The capital I and the small i has significance.

An internet (with a small i) is two or more network that communicate with each other. On the other hand, an Internet (with a capital I) is a collaboration of more than hundred and thousands of interconnected network which includes private individual, school, colleges and universities, research facilities, libraries, government agencies, facebook, twitter, google, etc.

Let us take an example. If you have your private network at home (consisting of your laptop, desktop, printer etc.) and if your neighbor has her private network (consisting of her computers, printer etc.) and if you both connect your private network together you get an internet.

When everyone connects their network together to form a huge network it is called the Internet also known as the Web.

IP address (Internet Protocol address) is an address assigned to each device connected to the Internet. It is a 32 bit binary address that uniquely and universally defines the connection of a host or a router. IP address is unique in the sense that no two devices connected to the Internet can have the same IP address. However, if a single device has two connections to the Internet via two networks, then it has two IP address. IP address is unique in the sense that the addressing system is accepted by any host that wants to connect to the Internet.

It is the total number of addresses used by the protocol. If the protocol has n bits to define an address then its address space is 2n as because each bit can have two different values 0 and 1.

For example, if a protocol uses 1 bit to define an address then its address space is 21 = 2

And the two addresses are 0 and 1.

Similarly, if a protocol uses 2 bits to define an address then its address space is 22 = 4.

00

01

10

11

We are using IP address that uses 32 bits to define an address of a device connected to the Internet. This addressing is called IPv4 or Internet Protocol Version 4. So for this protocol the address space is 232 = 4,294,967,296

And the 4,294,967,296 addresses are in binary form:

00000000 00000000 00000000 00000000

00000000 00000000 00000000 00000001

00000000 00000000 00000000 00000010

00000000 00000000 00000000 00000011

...

11111111 11111111 11111111 11111111

We generally use three common notations to show an IP address:

• Binary notation
• Dotted-Decimal notation

Binary Notation – In this notation the address bytes of the IP address is displayed as 32 bits. The address bits are arranged in octet separated by white space to make it more readable.

Example

01111100 01100000 00001010 00000100

Dotted-Decimal Notation – In this notation the address bytes of the IP address is displayed in decimal form separated by dots. Because each byte (octet) is of 8 bits so each number in the dotted-decimal notation is between 0 and 255.

Example

124.96.10.4

Example

7C600A04

IP addressing is of two types namely:

In Classful addressing the address space is divided into 5 classes A, B, C, D and E. Class A covers 1/2 of the address space. Class B covers 1/4 of the address space. Class C covers 1/8 of the address space. And class D and E covers 1/16 of the address space. Unfortunately this is a serious design flaw as the address space is not consumed properly.

A50%231 = 2,147,483,648
B 25% 230 = 1,073,741,824
C 12.5% 229 = 536,870,912
D 6.25% 228 = 268,435,456
E 6.25% 228 = 268,435,456

Recognizing classes

From binary notation

If the address starts with 0 then it belongs to class A.

If the address starts with 10 then it belongs to class B.

If the address starts with 110 then it belongs to Class C.

If the address starts with 1110 then it belongs to Class D.

If the address starts with 1111 then it belongs to Class E.

From dotted-decimal notation

Class A range from 0 to 127

Class B range from 128 to 191

Class C range from 192 to 223

Class D range from 224 to 239

Class E range from 240 to 255