IEC 60870-5 protocol in SCADA systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding IEC 60870-5-101 Frame Structure

Which part of the IEC 60870-5-101 frame contains the control field that manages the communication commands?

A Address field

B Start character

C Control field

D Checksum field

💡 Hint

Think about which part tells the device what action to perform.

The control field in IEC 60870-5-101 frames carries commands and responses that manage the communication session.

💻 Command Output

intermediate

Output of IEC 60870-5-104 Connection Establishment Command

What is the expected response code from a server after receiving a valid STARTDT (Start Data Transfer) command in IEC 60870-5-104?

SCADA systems

Client sends: STARTDT (Start Data Transfer) command
Server responds:

A STARTDT CON (Confirmation) frame

B STOPDT (Stop Data Transfer) command

C TESTFR (Test Frame) command

D RESETDT (Reset Data Transfer) command

💡 Hint

The server must confirm the start of data transfer.

After receiving STARTDT, the server replies with STARTDT CON to confirm data transfer start.

❓ Troubleshoot

advanced

Diagnosing IEC 60870-5-101 Communication Failure

A SCADA master device repeatedly fails to receive responses from a slave device over IEC 60870-5-101. Which of the following is the most likely cause?

A Incorrect ASDU address configured on the master

B Checksum field missing in the master's frames

C Master device not sending TESTFR commands periodically

D Slave device sending STARTDT CON without receiving STARTDT

💡 Hint

Check frame integrity and error detection.

The checksum field ensures frame integrity. Missing checksum causes the slave to reject frames, leading to no response.

🔀 Workflow

advanced

Sequence of Commands for Data Transfer in IEC 60870-5-104

What is the correct sequence of commands exchanged between a client and server to start data transfer in IEC 60870-5-104?

A Client sends STARTDT, Server sends STARTDT CON

B Server sends STARTDT, Client sends STARTDT CON, Server sends TESTFR

C Client sends TESTFR, Server sends STARTDT, Client sends STARTDT CON

D Client sends STARTDT, Server sends STARTDT CON, Client sends TESTFR

💡 Hint

Focus on the minimal handshake to start data transfer.

The client initiates with STARTDT, and the server confirms with STARTDT CON. TESTFR is used later for link testing.

✅ Best Practice

expert

Best Practice for Secure IEC 60870-5-104 Communication

Which of the following is the best practice to enhance security when deploying IEC 60870-5-104 protocol in a critical SCADA network?

A Allow unrestricted access from any IP to improve availability

B Disable all authentication to reduce latency

C Use default port 2404 without firewall restrictions

D Use VPN tunnels to encrypt communication between client and server

💡 Hint

Think about protecting data in transit over networks.

Using VPN tunnels encrypts data and protects against interception, which is critical for SCADA security.