TCP IP Model

TCP/IP is the communication protocol for communication between computers on the Internet. TCP/IP stands for Transmission Control Protocol / Internet Protocol. TCP/IP defines how electronic devices (like computers) should be connected to the Internet, and how data should be transmitted between them.

TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN. The IP component provides routing from the department to the enterprise network, then to regional networks, and finally to the global Internet. On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP to be robust and automatically recover from any node or phone line failure. This design allows the construction of very large networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed and uncorrected for long periods of time.

TCP provides reliable, accurate deli every of data to the correct destination. TCP is often referred to as connection-oriented. During transmission of data various packets are dropped or are lossed due to which the destination receives the incomplete data so in order to overcome this weakness TCP again request for the undelivered packet and that specific packet is delivered or transmitted again which makes TCP protocol suite to provides accurate transmission of data.
TCP/IP protocol suite consists of 4 layers which deal with their own type of protocols in order to perform specific functions. TCP/IP model was developed before OSI (Open System Interconnection) model due to which TCP/IP and OSI models do not match exactly with each other. TCP/IP 4 layers are as follows:
Link Layer. The link layer protocol suite is a combination of various link or physical protocols and standards. This layer deals with the network architecture, how different nodes are connected with each other, their physical connection and hardware.
Internet Layer. The internet layer provides the functionality of transportation of data from one end pc to another end pc (provided with destination IP address) or till the border of the network. The internet layer deals with most important protocol IP (Internet Protocol) as all data is encapsulated into packets (datagram).
Transport Layer. Transport layer protocol is a group of protocols and standards responsible for delivering data to the appropriate application. Transport layer actually encapsulates the application layer data in segments. These segments consist of application data added with Transport layer header. This header consists of socket.
Application Layer. Application Layer generally deals with the application specific protocols and methods and standards. These protocols provide various functionalities and feature to user including both local and remote applications

Each large company or university that subscribes to the Internet must have an intermediate level of network organization and expertise. A half dozen routers might be configured to connect several dozen departmental LANs in several buildings. All traffic outside the organization would typically be routed to a single connection to a regional network provider.

However, the end user can install TCP/IP on a personal computer without any knowledge of either the corporate or regional network. Three pieces of information are required:

The IP address assigned to this personal computer

The part of the IP address (the subnet mask) that distinguishes other machines on the same LAN (messages can be sent to them directly) from machines in other departments or elsewhere in the world (which are sent to a router machine)

The IP address of the router machine that connects this LAN to the rest of the world.