IPV4 Address

IPV4 Addresses

The IP layer of the TCP/IP protocol suite to identify the connection of each device to the Internet is called the Internet address or IP address. An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a host or a router to the Internet.

IPv4 addresses are unique in the sense that each address defines one, and only one, connection to the Internet. If a device has two connections to the Internet, via two networks, it has two IPv4 addresses. IPv4 addresses are universal in the sense that the addressing system must be accepted by any host that wants to be connected to the Internet.

Address Space

An address space is the total number of addresses used by the protocol. If a protocol uses b bits to define an address, the address space is 2^b because each bit can have two different values (0 or 1). IPv4 uses 32-bit addresses, which means that the address space is 2³² or 4,294,967,296 (more than four billion devices could be connected to the Internet.

Notations

There are two common notations to show an IPv4 address: binary notation, dotted-decimal notation .In binary notation, an IPv4 address is displayed as 32 bits. To make the address more readable, one or more spaces are usually inserted between each 8 bits. To make the IPv4 address more compact and easier to read, it is usually written in decimal form with a decimal point (dot) separating the bytes. This format is referred to as dotted-decimal notation. 

Hierarchy in Addressing

A 32-bit IPv4 address is also hierarchical, but divided into two parts. The first part of the address, called the prefix, defines the network; the second part of the address, called the suffix, defines the node connection of a device to the Internet.  Below Figure shows the prefix and suffix of a 32-bit IPv4 address. The prefix length is n bits and the suffix length is (32 − n) bits.

Classful Addressing

The whole address space was divided into five classes (class A, B, C, D, and E). This scheme is referred to as classful addressing.

In class A, the network length is 8 bits, but since the first bit, which is 0, defines the class, we can have only seven bits as the network identifier. This means there are only 2⁷= 128 networks in the world that can have a class A address.

In class B, the network length is 16 bits, but since the first two bits, which are (10)₂ define the class, we can have only 14 bits as the network identifier. This means there are only 2¹⁴= 16,384 networks in the world that can have a class B address

In class C, the network length is 24 bits, but since three bits define the class, we can have only 21 bits as the network identifier. This means there are 2²¹= 2,097,152 networks in the world that can have a class C address.

In class D, IP addresses belonging to class E are reserved for experimental and research purposes. 

        IP addresses of class E ranges from 240.0.0.0 – 255.255.255.254.In class E, addresses reserved for future use.