Internet Protocol (IP)

IP stands for Internet Protocol. It is responsible for sending data from one point to another on the Internet and is also used for Intranets. Every point or computer must have a unique IP address that gives an identity to that particular computer on the Internet. This unique address fo the sender as well as the destination machine is put on the data packet before sending and the Internet gateway decides where to send this packet based on this IP address. When all packets have arrived at the destination, the TCP keeps track of the dequence and puts al of them into a proper order so that the message or data is built up as was sent originally.

IP falls under the category of connectionless protocols which means that there is no permanent established connection between the sender and receiver of the message or data. In the Open Systems Interconnection (OSI) communication model, IP sits in the third layer called the networking layer. It is the responsibility f the Internet authorities to assign appropriate range of IP numbers to different organizations.
For an organization there are two sets of IP address. One is used to communicate with the outside world also known as the static IP. Other is used for internal use. The internal IP is not communicated outside the network limits andis usually called the internal IP address or subnet address.

The purpose and benefit  of a second set of IP addresses for internal use is that the second set makes it possible to address a large number of computers and other network devices or a grup of LANs that futher have a number of devices installed within an organization by the method of pooling the IP addresses.

The IP address are divided into four classes.
-> Class A addresses are for extremely large networks or gateways usually given at the level of one per country.
-> Class B addresses are of large networks or extremely large organiztions
-> Class C addresses are for small networks or may be for those at the level of organiztion
-> Class D addresses are also called multicast addresses, normally for representing devices and computers on the networks.

The class of addresses used by a device or network is identified by the first few bits of each IP address. The address structures look like this :

Class A 0 Networks (7 bits) Local address (24 bits)
Class B 10 Networks (14 bits) Local address (16 bits)
Class C 110 Networks (21 bits) Local address (8 bits)
Class D 1110 Networks (28 bits)