A COMPARATIVE STUDY OF IEC101, DNP3 and MODBUS SCADA PROTOCOLS

Abstract

In the last few decades, a new market appears as new horizon in the industrial field, “Automation” Understanding this subject is based on the data communication and related subjects, understanding Supervisory Control and Data Acquisition (SCADA) as an automation system need good knowledge of protocols that used for data exchange between different system terminals. Unfortunately SCADA protocols are so complex and need analytical mind to evaluate system performance, system behavior beside error handling .It is also difficult to answer the question of “which SCADA protocol to choose for a specific SCADA system”. In this research an analytical approach was employed to answer the most common questions regarding this subject where two dominant SCADA protocols are analyzed as master-to-substation protocol and one famous remote terminal unit (RTU)-intelligent electronic device (IED) protocol as an example. The researcher found that each protocol has an advantages and weak points for example at the time that DNP3 has more data objects IEC101 has more addressing capability, while DNP3 has more efficient security but the price is using about 11% of the link frame for security, at the same time IEC has less security method for only 0.4% of the total frame length. Information object addressing was also different between DNP3 and IEC101, while IEC101 uses an application level address, DNP3 do not, but this point makes analysis of DNP3 message difficult task, in practice this is a weak point. It was obvious that field bus protocol (MODBUS) requires only little group of data object.