Tuesday, 25 October 2011

data communication : IPv4 ADDRESSES

An IPv4 address is a 32-bit address that uniquely and universally defines the connection
of a device (for example, a computer or a router) to the Internet.

IPv4 addresses are unique. They are unique in the sense that each address defines
one, and only one, connection to the Internet. Two devices on the Internet can never
have the same address at the same time. We will see later that, by using some strategies,
an address may be assigned to a device for a time period and then taken away and
assigned to another device.
On the other hand, if a device operating at the network layer has m connections to
the Internet, it needs to have m addresses

The 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

A protocol such as IPv4 that defines addresses has an address space. An address space
is the total number of addresses used by the protocol. If a protocol uses N bits to define
an address, the address space is 2N because each bit can have two different values (0 or 1)
and N bits can have 2N values.

IPv4 uses 32-bit addresses, which means that the address space is 232 or
4,294,967,296 (more than 4 billion). This means that, theoretically, if there were no
restrictions, more than 4 billion devices could be connected to the Internet

Binary Notation
In binary notation, the IPv4 address is displayed as 32 bits. Each octet is often referred
to as a byte. So it is common to hear an IPv4 address referred to as a 32-bit address or a
4-byte address. The following is an example of an IPv4 address in binary notation:
          01110101 10010101 00011101 00000010

Dotted-Decimal Notation

To make the IPv4 address more compact and easier to read, Internet addresses are usu-
ally written in decimal form with a decimal point (dot) separating the bytes. The fol-
lowing is the dotted~decimal notation of the above address:

Reference :Data Communications and Networking By Behrouz A.Forouzan

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