Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

5
Fundamentals of
distributed network protocol
Objectives
When you have completed study of this chapter you should be able to:
• Relate the DNP3 model to the appropriate layers of the OSI model
• Describe the DNP3 protocol message structure
• Describe the operation of DNP3
5.1 Fundamental concepts
5.1.1 The OSI 7 layer model
The open systems interconnection model was defined by the International Standards
Organization (ISO). This model was a significant step in the development of standardization
of data communications systems. The OSI model presents data communications in a
hierarchical manner, starting at the bottom with the physical layer (layer 1), and moving to
the application layer (layer 7) at the top.