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TCP/IP Model

TCP/IP stands for Transmission control protocol/Internet protocol.TCP is a transport layer protocol and IP is a network layer protocol .TCP and IP both are different protocol but by the help of these two protocol ,TCP/IP model was developed.TCP/IP model defines how data is transferred from one computer to another.When two devices communicates with each other through the help of internet ,it is possible only for TCP/IP model .The TCP/IP model consists of 4 layers.These are :-

(1) Application layer:- 
-This layer performs the function of the   top three layer of the OSI model,i.e.Application layer , presentation   layer and session layer .
-The application layer is the top-most layer of the TCP/IP model.
-The application layer provides the user with the interface to communication.
-There are several protocols used by the application layer for interaction such as:FTP,HTTP, SMTP,DNS,TELNET etc.
-The application layer sends data to transport layer and receives data from transport layer .
(2) Transport layer:- 
-This layer is parallel the functions of OSI's Transport layer.
-The transport layer is responsible for end-to-end communication and error-free delivery of data.
-The two major protocols are used in transport later,i.e.TCP and UDP.
-The transmission control protocol (TCP) provides reliable, connection-oriented transport of data between two end-points on two computers that use internet protocol to communicate.
-The user datagram protocol (UDP) provides unreliable, connection less transport of data between two end-points on two computers that use internet protocol to communicate.
(3) Internet layer:- 
-This layer is parallel the functions of OSI's network layer .
-The main functions of this layer is logical addressing, Routing and path determination.
-IP addressing is done in network layer is called logical addressing.
-Routing is the method of moving data packets from source to destination .
-A Computer can be connected to Internet server in number of ways , choosing the best path for data delivery from source to destination is called path determination.
-The protocols used by this layer are ARP,ICMP,IGMP,RARP and IP.
-The internet layer communicates with transport later when receiving and sends data to the network access layer when transmitting.
(4) Network access layer:-
-This network access layer is the lowest layer of the TCP/IP model.
-This layer performs the functions of data link layer and physical layer of the OSI model.
-This layer is also called a network interface layer.
-It defines how the data should be sent physically through the network.
-This layer is mainly responsible for the transmission of the data between two devices on same network.
-The main protocols residing at this layer are: Ethernet,token ring ,FDDI etc.


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