International Standards Organization (ISO), faced the proliferation network of closed systems with a model defined as Open Systems Interconnection, or OSI model. It applies to all communication systems, from a personal computer operating within a network to exchange data between a satellite and its ground station.
Before standardization, many existing proprietary networks but was that a single manufacturer could not meet all the demands and supply all equipment for a relatively large company. There is then the reference model OSI accepted as international standard ISO 7498-1. Since then, he has worked continuously in the development of protocols based on this standard.
The OSI reference model is a modular structure that contains seven layers that govern the transmission of information between different systems as well as within a single system within a heterogeneous network. Each layer has a particular function. Communication is possible within a heterogeneous system where the tasks within a layer are performed according to standard.
The lower layers, govern communication between processors. With the help of these connections are established, through which, in any format data are channeled from their point of origin to destination.
The highest levels 5 ... 7 governing the communication between applications within the processors. Your task is to ensure that communication between the transmitting and receiving functions of the computer to work properly.
Figure 1.4 OSI Model
The following describes the functions of each layer of the OSI model. Also of course, the management layer is a part of the model that coordinates communication between the same layers:
PHYSICAL LAYER
Defines the mechanical, electrical and functional to establish and release physical connections that allow bits to transmit between extremes of physical media. Mechanical means to the shape and size of connectors, number of circuits and physical details.
Some electrical characteristics are the voltage levels used to represent the logic signals, impedance of the drivers, etc..
Among the functional characteristics are the speed of transmission and the function of each circuit. The physical layer determines the topology and the physical environment.
LINK LAYER
Should ensure the sending and receiving frames between. Seasons. It has two sublayers: the Medium Access Control (MAC), which defines the process by which multiple stations accessing the use of a shared physical environment, without causing interference between them and the line of logic control (LLC) establishing procedures for error-free transmission, including the check plots.
NETWORK LAYER
Add the information required to handle packets in a network with multiple paths. In this case there is more than one possible path for a message to go from one station to another. It is therefore necessary to define procedures for selecting the path followed by a message as well as procedures in case of traffic congestion on the road.
TRANSPORT LAYER
Divide the information to be transmitted in packets (to allow detection of errors in a more advantageous) while ensuring their proper order. This function is critical in a global network WAN, which usually packets arrive in a disorderly manner.
SESSION LAYER
Establishes procedures for both programs, residents between two computers, dialogue with each other. One of their services is the control of the dialogue.
PRESENTATION LAYER
Prepare the information transmitted for use in the application layer, making interpretations and data conversions required. These conversions typically can include ASCII and EBCDIC formats and encryption and decryption of information. Encryption of information is necessary for the transmission of confidential information in a public network such as WAN.
APPLICATION LAYER
Provides services gives end-users, providing access to information, such as terminal emulation, file transfer, email, etc..
And now, as we Integration with Industry l
We have seen above is an overview of the main features of a network, which applies both to an administrative network to an industrial network. From the standpoint of information transfer, efforts to integrate both, have led to development of tools both hardware and software.
Taking into account the different levels included in both cases, there is a hierarchical distribution based on business objectives and results of production:
Figure 1.5 Network Integration Industry
Below is an outline of an industrial network that includes devices and control equipment and its connection to the level of monitoring by computer. From this level, there is the possibility of integration with the administrative system:
