Network redundancy (ring topology) in SCADA systems - Mini Project: Build & Apply

Network redundancy (ring topology)

📖 Scenario: You are working with a SCADA system network that uses a ring topology to ensure network redundancy. This means each device is connected to two other devices, forming a closed loop. If one connection fails, data can still travel the other way around the ring.Your task is to represent this network in code and simulate checking the network's redundancy status.

🎯 Goal: Build a simple program that models a ring network of devices and checks if the network is redundant by verifying each device has exactly two connections.

📋 What You'll Learn

Create a dictionary called network with device names as keys and lists of connected devices as values.

Add a variable called expected_connections set to 2 to represent the ring topology requirement.

Write a loop to check each device's connections against expected_connections and store the results in a dictionary called redundancy_status.

Print the redundancy_status dictionary to show which devices have proper redundancy.

💡 Why This Matters

🌍 Real World

Ring topologies are common in SCADA systems to ensure continuous operation even if one connection fails.

💼 Career

Understanding network redundancy helps in maintaining reliable industrial control systems and troubleshooting network issues.

1

Create the network dictionary

Create a dictionary called network with these exact entries: 'DeviceA': ['DeviceB', 'DeviceE'], 'DeviceB': ['DeviceA', 'DeviceC'], 'DeviceC': ['DeviceB', 'DeviceD'], 'DeviceD': ['DeviceC', 'DeviceE'], 'DeviceE': ['DeviceD', 'DeviceA'].

SCADA systems

# Create the network dictionary with devices and their connections
# Your code here

Hint

Think of each device as a key and its connected devices as a list of values.

2

Set expected connections variable

Add a variable called expected_connections and set it to 2 to represent the number of connections each device should have in a ring topology.

SCADA systems

network = {
    'DeviceA': ['DeviceB', 'DeviceE'],
    'DeviceB': ['DeviceA', 'DeviceC'],
    'DeviceC': ['DeviceB', 'DeviceD'],
    'DeviceD': ['DeviceC', 'DeviceE'],
    'DeviceE': ['DeviceD', 'DeviceA']
}
# Set expected_connections to 2
# Your code here

Hint

Use a simple variable assignment to store the number 2.

3

Check redundancy for each device

Write a for loop using variables device and connections to iterate over network.items(). Inside the loop, create a dictionary called redundancy_status (before the loop) and add an entry for each device with value true if the length of connections equals expected_connections, otherwise false.

SCADA systems

network = {
    'DeviceA': ['DeviceB', 'DeviceE'],
    'DeviceB': ['DeviceA', 'DeviceC'],
    'DeviceC': ['DeviceB', 'DeviceD'],
    'DeviceD': ['DeviceC', 'DeviceE'],
    'DeviceE': ['DeviceD', 'DeviceA']
}
expected_connections = 2

# Create redundancy_status dictionary
redundancy_status = {}
# Use for loop to check connections
# Your code here

Hint

Initialize the dictionary before the loop. Use len(connections) to count connections.

4

Print the redundancy status

Write a print statement to display the redundancy_status dictionary.

SCADA systems

network = {
    'DeviceA': ['DeviceB', 'DeviceE'],
    'DeviceB': ['DeviceA', 'DeviceC'],
    'DeviceC': ['DeviceB', 'DeviceD'],
    'DeviceD': ['DeviceC', 'DeviceE'],
    'DeviceE': ['DeviceD', 'DeviceA']
}
expected_connections = 2

redundancy_status = {}
for device, connections in network.items():
    redundancy_status[device] = (len(connections) == expected_connections)

# Print the redundancy_status dictionary
# Your code here

Hint

Use print(redundancy_status) to show the results.

Practice

1. What is the main advantage of using a ring topology in SCADA network redundancy?

easy

A. It provides a closed loop that allows data to travel in both directions for fault tolerance.

B. It reduces the number of cables needed compared to a star topology.

C. It eliminates the need for switches or routers in the network.

D. It ensures that only one device controls the entire network.

Solution

1. Step 1: Understand ring topology structure

   A ring topology connects devices in a closed loop, allowing data to flow in both directions.

2. Step 2: Identify redundancy benefit

   This loop allows the network to continue operating even if one connection breaks, providing fault tolerance.

3. Final Answer:

   It provides a closed loop that allows data to travel in both directions for fault tolerance. -> Option A

4. Quick Check:

   Ring topology = fault tolerance loop [OK]

Hint: Ring means loop for backup path [OK]

Common Mistakes:

• Thinking ring topology reduces cables more than star
• Believing ring removes need for switches
• Assuming one device controls whole network

2. Which of the following is the correct description of RSTP in a ring topology?

easy

A. RSTP disables all redundant links permanently to avoid loops.

B. RSTP requires manual configuration of backup routes in the ring.

C. RSTP quickly blocks and unblocks links to prevent loops and maintain redundancy.

D. RSTP only works in star topologies, not ring topologies.

Solution

1. Step 1: Understand RSTP function

   Rapid Spanning Tree Protocol (RSTP) manages network loops by blocking and unblocking links dynamically.

2. Step 2: Apply to ring topology

   In ring topology, RSTP prevents loops while keeping backup paths ready for fast recovery.

3. Final Answer:

   RSTP quickly blocks and unblocks links to prevent loops and maintain redundancy. -> Option C

4. Quick Check:

   RSTP = dynamic loop prevention [OK]

Hint: RSTP blocks loops fast, keeps backups ready [OK]

Common Mistakes:

• Thinking RSTP disables all backups permanently
• Believing RSTP needs manual backup setup
• Assuming RSTP only works in star topology

3. Given a ring network with 4 devices A, B, C, D connected in order, if the link between B and C fails, what happens to the data flow?

medium

A. Data flow stops completely until the link is repaired.

B. Data reroutes from B to A to D to C, maintaining communication.

C. Data flows only between A and B, and between C and D separately.

D. Data flows directly from B to C using a backup cable.

Solution

1. Step 1: Identify ring topology behavior on failure

   In a ring, if one link breaks, data can travel the opposite way around the loop.

2. Step 2: Trace data rerouting path

   With B-C link down, data from B goes back to A, then to D, and finally to C, keeping communication alive.

3. Final Answer:

   Data reroutes from B to A to D to C, maintaining communication. -> Option B

4. Quick Check:

   Ring reroutes data opposite way on failure [OK]

Hint: Ring sends data opposite way if link breaks [OK]

Common Mistakes:

• Assuming data stops completely on one link failure
• Thinking devices split into isolated pairs
• Believing backup cable exists physically between B and C

4. A SCADA ring network is experiencing a broadcast storm causing network slowdown. What is the most likely cause?

medium

A. RSTP is not enabled, causing loops to flood the network.

B. All devices are configured with unique MAC addresses.

C. The ring topology has only one device connected.

D. The network cables are too long, causing signal loss.

Solution

1. Step 1: Understand broadcast storm cause

   Broadcast storms happen when loops cause packets to circulate endlessly, flooding the network.

2. Step 2: Identify missing loop prevention

   Without RSTP or similar protocol, ring loops cause broadcast storms.

3. Final Answer:

   RSTP is not enabled, causing loops to flood the network. -> Option A

4. Quick Check:

   Missing RSTP = broadcast storm [OK]

Hint: No RSTP means loops cause storms [OK]

Common Mistakes:

• Thinking unique MAC addresses cause storms
• Assuming single device causes broadcast storm
• Blaming cable length for broadcast storms

5. In a SCADA ring topology with RSTP enabled, if two links fail simultaneously on opposite sides of the ring, what is the expected network behavior?

hard

A. The network remains fully operational with no data loss.

B. All devices shut down to prevent damage.

C. RSTP automatically repairs both links instantly to restore the ring.

D. The ring breaks into two isolated segments, causing partial network failure.

Solution

1. Step 1: Analyze double link failure in ring

   Two opposite link failures break the ring into two separate parts.

2. Step 2: Understand RSTP limits

   RSTP can block or unblock links but cannot repair physical breaks instantly.

3. Step 3: Predict network state

   Network splits into two isolated segments, causing partial failure.

4. Final Answer:

   The ring breaks into two isolated segments, causing partial network failure. -> Option D

5. Quick Check:

   Two breaks = network splits [OK]

Hint: Two breaks split ring, partial failure [OK]

Common Mistakes:

• Assuming RSTP fixes physical cable breaks instantly
• Believing network stays fully operational
• Thinking devices shut down automatically