INTRODUCTION:

• Usually, computers communicate through the Internet. The packet transmitted by the sending computer may pass through severallocal ara network before reaching the destination computer.
• For this level of communication, a global addressing scheme is required so that it is globally recognized rather then locally; we call this logical addressing,In modern world the term Internet Protocol address is used to mean a logical address in the network layer of the network.
• This protocol suite. addresses are of two versions namely the Internet Protocol version four and IP version six.The Internet Protocol version four is commonly prefered in todays world,though in near future moving into version six has been recommended due to large number of people getting connected to internet everyday.
• Internet Protocol version four is a 32-bit version protocol.It has an address space of 232 address spaces.
• Each address is unique in the sense that it defines one and only one computer that is connected to the internet.Comparing Internet Protocol version four with Internet Protocol version six,Internet Protocol version six is a 128-bit address.Anaddress space defines the total number of addresses used by the protocol.
• In genearal 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.

There are three notations to IPv4 addresses namely:

1. THE BINARY NOTATION OF REPRESENTING THE IP ADDRESS:

• In binary notation, the Internet Protocol version four address is displayed as 32 bits. Each octet is often referred to as a byte. So it is common to hear an Internet Protocol version four address referred to as a 32-bit address or a four-byte address. The following is an example of an IPv4 address in binary notation

$10000000.00110010.00101100.00111100$

• Usually an IP address has four parts which are divided into four octets meaning each individual part of IP address is divided into bits of Eight.

   

2. THE DOTTED DECIMAL NOTATION REPRESENTATION OF IP ADDRESS:

• To make the IPv4 address more compact and easier to read, Internet addresses are usually written in decimal form with a decimal point (dot) separating the bytes. The following is the dotted~decimal notation of an ip address

$192.168.1.1$

• Each byte (octet) is 8 bits, but in case of Dotted DecimalNotation each number in dotted-decimal notation is a value ranging from0 to 255.

   

3. THE HOST ID AND NET ID IN IINTERNET PROTOCOL(IP) ADDRESS:

• In classful addressing, an IP address of class A,B and C is divided into two parts : netid and hostid.The netid and hostid are of varying lengths, depending on the class of the address.

1. Netid: The part of an IP address that identifies the network.
2. Hostid: The part of an IP address that identifies a host in a network In class A, one byte defines the netid and three bytes define the hostid. In class B, two bytes define the netid and two bytes define the hostid. In class C, three bytes define the netid and one byte defines the hostid.

Example:

1. Let us consider any ip address between 0 to 255:84.42.58.11
2. Binary Notation of IP address can be gven as:01010100 00101010 00111010 00001011
3. This address is aclass A IP address.
4. The network address of this Class A IP address is84.0.0.0
5. The host addresses of this Class A IP address is0.42.58.11

CLASSFUL ADDRESSING:

• IPv4 addressing uses the concept of classes.This architecture is called classful addressing.In classful addressing, the address space is divided into five classes: A, B, C, D, and E. Each class occupies some part of the address space.It is possible to find the class of an address when given the address in binary notation or dotted-decimal notation. If the address is given in binary notation, then first bits represent what class the Internet Protocol (IP)address belongs to. If the address is given in decimal-dotted notation, the first byte defines the class.

PROBLEMS IN CLASSFUL ADDRESSING OF INTERNET PROTOCOL ADDRESS:

• One problem with classful addressing is that each class is divided into a fixed number of blocks with each block having a fixed size

• Class A addresses were designed for large organizations with a large number of attached hosts or routers. Class B addresses were designed for midsize organizations with tens of thousands of attached hosts or routers.
• Class C addresses were designed for small organizations with a small number of attached hosts.A block in class A address is too large for almost any organization. This means most of the addresses in class A were wasted and were not used.
• A block in class B is also very large, probably too large for many of the organizations that received a class B block. A block in class C is probably too small for many organizations.

MASK IN AN INTERNET PROTOCOL(IP) ADDRESS:

• Although the length of the netid and hostid is predetermined in classful addressing, we can also use a mask , a 32-bit number made of contiguous Is followed by contiguous 0s.
• The mask can help us to find the netid and the hostid.
• For example, the mask for a class A address has eight 1s, which means the first 8 bits of any address in class A define the netid; the next 24 bits define the hostid.

• The last column in above table shows the mask in /n notation where n can be 8, 16, or 24 in classful addressing.

• This notation is also called slash notation or Classless Interdomain Routing notation. The notation is used in classless addressing.

   

SUBNETTING OF AN INTERNET PROTOCOL(IP) ADDRESS:

• During the era of classful addressing, subnetting was introduced.
• If an organization was granted a large block in class A or B, it could divide the addresses into several contiguous groups and assign each group to smaller networks or, in rare cases, share part of the addresses with neighbors.

• Subnetting increases the number of Is in the mask.

   

SUPERNETTING OF INTERNET PROTOCOL(IP) ADDRESS:

• In supernetting, an organization can combine several blocks of an IP address say class C blocks to create a larger range of addresses. In other words, several networks are combined to create a supernetwork or a supemet.
• An organization can apply for a set of class C blocks instead of just one. For example, an organization that needs 1000 addresses can be granted four contiguous class C blocks.

• The organization can then use these addresses to create one supernetwork. Supernetting decreases the number of Is in the mask.

   

ADDRESS DEPLETION IN AN INTERNET PROTOCOL(IP) ADDRESS:

• The flaws in classful addressing scheme combined with the fast growth of the Internet led to the near depletion of the available addresses.

• Yet the number of devices on the Internet is much less than the 232 address space.Classes A and B have run out of addresses and a class C block is too small for most midsize organizations.One solution to the problem is Classless Addressing.

   

CLASSLESS ADDRESSING:SOLVING THE PROBLEM OF CLASSFULL ADDRESSING:

• In classless addressing, when an entity, small or large, needs to be connected to the Internet, it is granted a block of addresses.
• The size of the block varies based on the nature and size of the entity.
• For example, a household may be given only two addresses; a large organization may be given thousands of addresses.
• An ISP, as the Internet service provider, may be given thousands or hundreds of thousands based on the number of customers it may serve.