Industrial Lightweight Overlay (Ilo)

This repository contains the source code and experimental data for the research paper: "Enabling Zero-Touch Certificate Management in Modular Plants through Overlay Networks".

Project Overview

This project investigates whether Overlay Networks (ONs) can provide a lightweight, deterministic addressing and routing substrate inside modular plants (specifically "Production Gray Boxes") to enable zero-touch certificate management. The code implements three structured overlay topologies suitable for Operational Technology (OT) environments:

1. Chord (Ring-based)
2. Kademlia (Tree-based/XOR metric)
3. CAN (Content Addressable Network / Space-based)

The implementation focuses on resource efficiency and feasibility within automation systems, utilizing Beremiz (Soft-PLC) for the nodes and Siemens TIA Portal for the orchestration interface.

Hardware & Software Architecture

The code is designed for a specific hardware demonstrator setup described in the associated paper:

• Nodes: 5x Raspberry Pi 4B units running Ubuntu 22.04.5 LTS.
• Orchestrator: 1x Siemens S7-1500 PLC.
• Network: Star topology via a managed Ethernet switch.
• Communication: Modbus TCP is used for communication between nodes and the PLC.

Software Stack

• Runtime: Beremiz (Python-based IEC 61131-3 Soft-PLC).
• Middleware: Node-RED (handling S7 and Modbus-TCP translation).
• Engineering: Siemens TIA Portal V18.

Repository Content

1. Nodes (Beremiz Code)

This directory contains the Beremiz projects for the three supported overlay algorithms.

• Variants:
  • Naive (e.g., Chord_N1): Uses conservative timing margins (2s timer delays, 500ms cyclic tasks) to ensure stability without acknowledgement messages.
  • Optimized (e.g., Chord_N1_opt): Features reduced timing margins (1s timer, 250ms cyclic tasks) and proximity-aware NodeID assignment to demonstrate performance headroom.
• Subdirectories:
  • Chord / Chord optimised: Ring topology implementation.
  • Kademlia / Kademlia optimised: Tree topology using XOR metrics.
  • CAN / CAN optimised: d-dimensional coordinate space implementation.

2. Node-RED

Contains the flow definitions for routing messages between the PLC and the Soft-PLC nodes.

• CAN_NodeRED.json
• Chord_NodeRED.json
• Kad_NodeRED.json

3. TIA - Project

Contains the orchestration logic for the Siemens S7-1500.

• P2P.zap18: Archived TIA Portal V18 project file.

4. Evaluation

Contains validation data regarding the join/leave procedures and resource impact.

• RawData: Logs from the experimental runs.
• Scenarios: Excel files and scripts used to calculate recovery times and state durations.

How to Run the Demonstrator

Prerequisites

• 5x Raspberry Pis configured with Beremiz and Node-RED.
• 1x Siemens S7-1500 PLC connected to the network.
• Engineering PC with TIA Portal V18.

Step 1: Start the Soft-PLCs (Raspberry Pis)

Perform this step on each of the 5 Raspberry Pi nodes.

1. Navigate to the Beremiz directory and launch the IDE:

cd Beremiz/beremiz/
python3 Beremiz.py

2. Open the specific Project File corresponding to the node number and algorithm (e.g., Chord_N1).
3. Build & Connect:
   • Click "Build project in build folder".
   • Click the Green Plug icon to connect to the local PLC runtime.
   • Click the Yellow Arrow to transfer the code.
   • Click the Running Man icon to start the execution.

Step 2: Start Node-RED (Communication Layer)

1. Access Raspberry Pi 1 (physically located as the uppermost unit on the IRS demonstrator).
2. Start Node-RED.
3. Import and select the JSON flow corresponding to the network being tested (e.g., Chord_NodeRED.json).
4. Verification: Check if all nodes are online. On the physical demonstrator, a green light below the node indicates valid data transfer.

Step 3: TIA Portal Orchestration

1. Open P2P.zap18 in TIA Portal V18.
2. Connect to the physical S7-1500 PLC.
3. State Check:
   • Inspect the Data Blocks (DBs) responsible for "Bootstrap" and "Leave" procedures.
   • Ensure the variable State is set to 0. If not, force the value to 0.
   • Ensure variables Join and Leave are set to false.

Step 4: Operation via HMI

The system is controlled via the HMI connected to the PLC (or the TIA Portal HMI simulation).

1. Activate Simulation: Press "Activate simulation" to enable the state display lights on the physical rig.
2. Join Procedure:
   • Press Join Procedure. This triggers the JoinCtrl signal in the function blocks.
   • The nodes will transition through Init -> Joining -> Online states.
3. Manual Operation:
   • Once joined, click buttons Node 2 to Node 5 to view network details in a pop-up window.
   • You may manually trigger "Join" or "Leave" signals for specific nodes to simulate churn.
4. Leave Procedure:
   • Press Leave Procedure to trigger the graceful exit sequence (LeaveCtrl).

Citation

If you use this code or data in your research, please cite the authors.