This article describes the reference model TCP / IP, which is the historical and technical standard of the Internet.
The U.S. Department of Defense has established the Reference Model TCP / IP because he needed to design a network that can withstand all conditions, even a nuclear war. In a world connected by various types of communication media such as the son of copper, microwave, fiber optics and satellite links, the Defense Department wanted a packet transmission capable of reaching and certainly in any what conditions. This problem of extremely ambitious design led to the creation of the model TCP / IP.
The different layers
Unlike proprietary network technologies mentioned above, TCP / IP was developed as an open standard. This meant that anyone could use TCP / IP. This helped to accelerate the development of TCP / IP as standard.
Model TCP / IP includes the following four layers:
The application layer
The transport layer
The Internet layer
The access layer network
Although some layers of the model TCP / IP have the same name as the layers of the OSI model *, they do not match exactly. It should be noted that the application layer provides different functions in each model.
The designers of the model TCP / IP felt that the application layer should include details of the session and presentation layers OSI *. They created an application layer that handles issues of representation, the code and control the dialogue.
The transport layer is responsible for quality issues related to service reliability, flow control and error correction. One of its protocols, TCP (Transmission Control Protocol - Protocol Transmission Control), provides an excellent means of creating flexible, reliable communications network, moving well and showing an error rate low.
TCP is connection oriented. It maintains a dialogue between your source and destination computer while he prepares the application layer information into units called segments. A connection oriented protocol does not mean that there is a circuit between computers in communication. This type of operation indicates that there is an exchange of segments of layer 4 between the two host computers to confirm the existence of the logical connection for a while.
The objective of the Internet layer is to divide TCP segments into packets and send them from any network. Packets to the network regardless of destination of the path they have taken to get there. The protocol that governs this layer is called Internet Protocol (IP). Determining the best path and packet switching occur at this layer.
The relationship between IP and TCP is essential. Each protocol has a special role: IP points to the path for the packets, while TCP provides a reliable transport.