Thursday, September 24, 2015

Learn to Know How does The SCADA Protocol Works to Operate the Control Points

In a control system remote terminal unit (RTU) is designed to correlate with the SCADA master station database and serves to connect the sensor to the server in the data transfer process, converting sensor signals into digital data and sends digital data to the control system. In general, a SCADA system always refers to a system that coordinates, but does not control the process in real time and it represents the predominant SCADA systems and protocols in use in the utility industry today.
SCADA communication is regulated through a protocol that works between the host and the RTU form a viable model for the RTU to intelligent electronic devices (IED) communication. If the antiquity used a proprietary protocol in accordance with its SCADA manufacturers, now there are already some established protocol standards, so no need to worry about compatibility issues of communication again.
Currently, in the industry, there several different protocols used. The most popular are as below:
  • The Distributed Network Protocol version 3 (DNP3).
  • The International Electrotechnical Commission (IEC) 60870-5 series, especially IEC 60870-5-101 (commonly called as 101)

DNP3 Client Server Relationship

Distributed Network Protocol version 3 (DNP3)

SCADA protocols are designed to be very compact. Many are designed to send information only when the master station polls the RTU which is situated between the Open System Interconnection (OSI) application layer and the application program.
Many of these protocols such as DNP3 used for transmission of data from point A to point B using serial communications now contain extensions to operate over TCP / IP. Although some believe that the security of good engineering practice to avoid connecting SCADA systems to the Internet so the attack surface is reduced, many industries, such as wastewater collection and water distribution, have been using the existing cellular network infrastructure to monitor them along with internet portal for late-data the delivery and modification. Cellular data network based on thethree-layer enhanced performance architecture (EPA) model contained in the IEC 60870-5 standards is encrypted before transmission over the Internet.

IEC 60870-5-101

Because most sensor and control relays are just simple electrical equipment, such tools can not generate or translate the communication protocol. Thus it takes RTU bridge between the sensors and the SCADA network. RTU changing sensor inputs to the relevant protocol format such as IEC 60870-5 specifies a number of frame formats and services that may be provided at different layers and sends it to the master SCADA. Enhanced Performance Architecture (EPA) reference model for efficient implementation within RTUs (RTU besides also receive commands in protocol format and gives a corresponding electrical signal to control the respective relays), meters, relays, and other Intelligent Electronic Devices (IEDs).


Due to the use of standard protocols and the fact that many network SCADA system can be accessed from the Internet, a system that is potentially vulnerable to remote cyber attacks. On the other hand, the use of standard protocols and technical security means that security fixes are applicable standard for SCADA system, assuming they receive timely treatment and update.
The use of the Distributed Network Protocol version 3 (DNP3) and the IEC 60870-5-101 protocol  has several advantages such as High data integrity, Flexible structure, Multiple applications, Minimized overhead and Open standard.


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