Zakaria El Intissar

I'm an automation and industrial computing engineer with 12 years of experience in power system automation, SCADA communication protocols, and electrical protection. I build tools and write guides for Modbus, DNP3, IEC 101/103/104, and IEC 61850 on ScadaProtocols.com to help engineers decode, analyze, and troubleshoot real industrial communication systems.

Author Archives: Zakaria El Intissar

How to Monitor SCADA Protocol Traffic (Modbus RTU/TCP, IEC-104, DNP3, IEC-61850)

Monitoring SCADA protocol traffic is essential for diagnosing field issues, validating protocol behavior, troubleshooting mapping or timing problems, and improving the reliability of industrial automation systems. Whether the system uses legacy serial-based protocols such as Modbus RTU, IEC 60870-5-101, or DNP3 Serial, or modern TCP/IP-based protocols such as Modbus TCP, IEC 60870-5-104, DNP3 TCP, or IEC 61850, having… Read More »

IEC 104 News 2026: Standard Updates, Security & NIS2 Compliance

IEC 60870-5-104, commonly called IEC 104, remains one of the most widely deployed telecontrol protocols in power system SCADA networks worldwide. It extends IEC 60870-5-101 for operation over TCP/IP, enabling real-time data exchange between control centers and remote terminal units (RTUs) in electrical engineering and power system automation applications. As of early 2026, the IEC 104 base protocol… Read More »

IEC 60870-5-104 ASDU Structure Explained — Fields and Format

The Application Service Data Unit (ASDU) is the core of the IEC 60870-5-104 communication protocol. It defines how information is represented and exchanged between a controlling station (SCADA master) and controlled stations such as RTUs or IEDs. If the Application Protocol Data Unit (APDU) is the message envelope, the ASDU is the payload — carrying the actual telemetry… Read More »

DNP3 vs IEC 60870-5-104: Which Protocol Is Better for SCADA?

In modern SCADA (Supervisory Control and Data Acquisition) systems, choosing the right communication protocol can determine how efficiently, securely, and reliably data moves between control centers and field equipment. Two of the most widely used open standards are DNP3 (Distributed Network Protocol version 3) and IEC 60870-5-104. While both were designed for real-time monitoring and control, they differ… Read More »

DNP3 Secure Authentication Version 6 (SAv6): Encryption and Authorization Explained

Modern SCADA and utility automation systems face growing cybersecurity demands. The Distributed Network Protocol (DNP3)—the backbone of many control networks—has evolved to meet them. With the release of IEEE 1815-2020, the DNP3 Secure Authentication Version 6 (SAv6) specification brings authenticated encryption, centralized authorization, and simplified key management directly into the protocol. This article explains how SAv6 improves on… Read More »

DNP3 Port Number Explained: TCP/UDP 20000, Secure Port 19999, and Firewall Configuration

DNP3 runs over IP networks using TCP or UDP port 20000. This port number is the standard for communication between SCADA masters and field devices (RTUs, IEDs) in electric utilities, water systems, and oil and gas pipelines. The IANA also registered port 19999 for DNP3 Secure (DNP3 over TLS), though it is rarely used in practice — most… Read More »

DNP3 Report by Exception, Background Polls, and Balanced Communication

The Distributed Network Protocol (DNP3) is recognised for its efficiency and reliability in SCADA and power automation systems. The DNP3 protocol is characterized by three key operational concepts: Report by Exception, Periodic Background Polls, and Balanced Communication. These concepts enable the system to optimize bandwidth utilization while ensuring real-time monitoring of field device status. Report by Exception (unsolicited… Read More »

Modbus over RS485 Communication Frequency | Recommended Baud Rates & Best Practices

In industrial automation, Modbus over RS-485 is still one of the most popular and reliable ways to connect programmable logic controllers (PLCs), sensors, meters, and field devices. One key parameter that determines how well this network performs is the communication frequency. this is also called the baud rate. It defines how fast data is transmitted between Modbus master… Read More »

DNP3 System Topology Explained: Master, Multidrop, and Hierarchical

In a DNP3-based SCADA system, system topology refers to the physical and logical arrangement of how master stations, outstations, and communication devices are connected and interact. Designed for flexibility and reliability, DNP3 supports multiple network configurations that can be tailored to the system size, communication medium, and redundancy requirements. The most common DNP3 topologies include master–slave, multidrop, hierarchical,… Read More »

Link Initialization in IEC 60870-5-101 | Master-Slave Communication Setup

Before any data or command exchange can begin, the communication link between the controlling station (master) and controlled stations (RTUs or substation gateways) must be properly established. This process — called link initialization — ensures both sides start from a synchronized state with correct frame sequencing, clear buffers, and ready communication paths. Link initialization is part of the… Read More »