The OSI reference model in automobiles

Since the OSI reference model can describe all modes and types of communication, it must also apply to functions for complex communications systems. Since simpler communications systems do not have all the functions available, all the layers are not necessary here. Under these circumstances the model can also have empty layers.
Therefore only three layers are necessary for data communication in the automation and field areas. All types of field bus systems belong to this, even the bus systems in automobiles:

• Physical Layer, Layer 1
  Here the actual transport of data takes place. Therefore all the electrical, mechanical, operational and procedural parameters are established in this layer.
   
• The Data Link Layer, Layer 2
  Here the data transmission between two devices is co-ordinated. Therefore error detection and correction play a big role. For this purpose data is separated into packets and given a test sequence. If there are errors in transmission the signalling is repeated.
   
• The Application Layer, Layer 7
  The application layer provides services with which the communication system or the transmitted data can be accessed. It constitutes a system overlapping interface and is the beginning or end point of a communication system.