Traditional SCADA (WinCC, iFIX, Wonderware) vs. Cloud-Based IIoT Platform (Eziwan + cloud)
| Criterion | Traditional SCADA | IIoT (Eziwan + Cloud) |
|---|---|---|
| Main Architecture | Centralized (server + clients) | Distributed (edge + cloud) |
| Standardization of Protocols | ✓ Forte (OPC-UA, IEC 61968, DNP3) | Variable (MQTT, REST, OPC-UA) |
| Initial deployment cost | ✗ High (30k to 500k€) | ✓ Moderate (a few thousand euros per site) |
| Scalability | ✗ Limited (point-based licenses/tags) | ✓ Horizontal, cloud-native |
| Control Latency | ✓ < 100 ms (real time) | ✗ 50–500 ms (monitoring) |
| Purdue Model | Levels 2–3 (supervision/monitoring) | Level 3.5/4 (analytics/cloud) |
| Data History | On-premises historian (OSIsoft PI, etc.) | ✓ Cloud time series (InfluxDB, AWS) |
| Cybersecurity Architecture | ✓ Air-gap OT, isolated network | Internet + VPN with zero inbound ports |
| Infrastructure Maintenance | ✗ Resource-intensive (local servers, licenses) | ✓ Minimal (OTA firmware, cloud) |
| Cloud Integration / Analytics | ✗ Complex (specific connectors) | ✓ Native (REST API, MQTT) |
| OPC-UA Integration | ✓ Standard (native server) | ✓ OPC-UA Client (Eziwan Gateway) |
| Deployment time | ✗ Months to Years (Engineering) | ✓ Days to Weeks (ZTP) |
| Technological Maturity | ✓ Very mature (30+ years old) | Growing rapidly |
| Total cost over 5 years (10 sites) | ✗ 200k to 2M€ | ✓ 50k to 200k€ |
| Off-site mobile access | Via a dedicated VPN client | ✓ Web browser or mobile app |
8 Dimensions for Understanding SCADA and IIoT in Their Real-World Context
SCADA (Supervisory Control and Data Acquisition) has been the standard for industrial monitoring since the 1970s. It monitors and controls industrial processes in near real time, including water distribution and wastewater treatment, power grids, petrochemicals, and transportation. Its strengths include reliability, redundancy, standardized protocols (OPC-UA, DNP3, IEC 61850), and a proven architecture. Major vendors—Siemens WinCC, AVEVA (formerly Wonderware) InTouch, GE Proficy iFIX, and Ignition by Inductive Automation—offer scalable solutions ranging from 100 to several million data points.
The IIoT (Industrial Internet of Things) is not a single software solution but an architecture: sensors and devices connected to edge gateways (such as Eziwan) that transmit data to cloud platforms for analytics, visualization, and remote access. The IIoT excels in areas where SCADA is limited: multiple, geographically dispersed sites; remote access via smartphone or browser; and integration with business tools (ERP, BI, predictive maintenance). The adoption curve is faster, the startup cost is lower, and scalability is virtually unlimited.
OPC-UA (IEC 62541) is the key technology that enables these two worlds to coexist. As an industrial interoperability standard with native security (TLS, certificate authentication), an object information model, and IP transport, OPC-UA is adopted by all major SCADA vendors and PLC manufacturers (Siemens S7-1500, Schneider M580, Rockwell ControlLogix). Eziwan implements an OPC-UA client capable of reading data from an OPC-UA SCADA or PLC server and uploading it to the cloud, creating a natural bridge between on-premises SCADA architecture and the cloud-based IIoT layer.
SCADA historians (OSIsoft PI System, AVEVA PI, GE Proficy Historian) are specialized databases for process history data, featuring proprietary compression (SwingDoor for PI), access via the PI Web API or SQL, and native integration with SCADA systems. They operate on-premises with per-tag licensing, which becomes costly at scale. Cloud-based time-series databases (InfluxDB, TimescaleDB, AWS Timestream, Azure ADX) are open-source or SaaS, with costs proportional to the volume ingested, unlimited horizontal scalability, and standard REST/MQTT APIs. Eziwan writes directly to InfluxDB or TimescaleDB via its native write protocol, simplifying the data architecture.
The Purdue model (ISA-95) organizes OT systems into isolated zones: the OT network (levels 0–3) is separated from the IT network (levels 4–5) by a DMZ (level 3.5). This model ensures isolation but complicates remote access. The IIoT with the Eziwan gateway adheres to this model: the gateway establishes only an outbound connection (zero-inbound-port) via OpenVPN to the cloud, without opening any inbound ports on the OT network. The SCADA network remains physically isolated, and remote access is carried out via the strictly controlled OpenVPN tunnel. This is the architecture recommended by ANSSI for connecting critical industrial systems to the cloud.
The vast majority of industrial sites are brownfield sites—they already have an operational SCADA system, sometimes as old as 15 years, that cannot be replaced without significant operational risk. The smart IIoT approach involves leaving the SCADA system untouched and adding a parallel connectivity layer. Eziwan connects to industrial equipment (PLCs, RTUs) via Modbus, independently of the SCADA system, and uploads the data to the cloud. The result: local SCADA monitoring is maintained, along with cloud-based IIoT analytics, without disrupting the existing system. This brownfield approach is the most common in industrial digitalization projects in France.
The IIoT cloud cost includes: the Eziwan gateway (800 to 1,500 euros per site), the cloud subscription (50 to 200 euros per site per month), and time-series storage costs (which vary depending on volume). Over 3 years for 10 sites: 15,000 to 30,000 euros CAPEX + 18,000 to 72,000 euros OPEX = 33,000 to 102,000 euros TCO. A comparable on-premises SCADA system (WinCC, 10 sites): licenses 50,000 to 200,000 euros, servers 20,000 euros, engineering 50,000 euros, annual maintenance 15,000 euros = 185,000 to 410,000 euros over 3 years. Cloud-based IIoT offers a TCO that is 3 to 5 times lower for multi-site monitoring scenarios.
The emerging hybrid architecture combines on-premises SCADA for mission-critical real-time control and cloud-based IIoT for analytics, remote access, and ERP integration. SCADA monitors and controls locally via OPC-UA. The Eziwan gateway reads the SCADA’s OPC-UA data and sends it to the cloud for analytics and remote access. This architecture preserves SCADA’s real-time and security guarantees while leveraging the scalability and accessibility of the IIoT cloud. It is the architecture recommended by Industry 4.0 and RAMI 4.0 (Reference Architecture Model for Industry 4.0).
4 Real-World Architectures Illustrating the Complementary Roles of SCADA and IIoT
Background: Water utility operating a treatment plant (Wonderware SCADA) and 40 scattered pumping stations
The main station retains its Wonderware SCADA system for real-time process control (chlorination, filtration, turbidity). The 40 dispersed pumping stations, which do not have local SCADA systems, are monitored via Eziwan 4G gateways. The Eziwan cloud dashboard consolidates data from the 40 stations and provides SMS and email alerts. An OPC-UA bridge connects the central SCADA system to the cloud platform, providing a unified view. IIoT remote monitoring has reduced service calls by 70%.
Background: Plastic parts manufacturer with 12 injection molding machines and no existing monitoring system
Without the budget for a full SCADA system (at least 60,000 euros), the SME deployed three Eziwan gateways to monitor the 12 presses via Modbus TCP. The cloud-based dashboard displays production rates, energy consumption, and downtime in real time. Process deviation alerts are sent to team leaders via smartphone. ROI was achieved in 8 months thanks to a reduction in unplanned downtime and optimized electricity consumption.
Background: Refining unit with Siemens WinCC SCADA for process control and predictive analytics requirements
The WinCC SCADA system manages real-time control of the unit (pressure, temperature, flow) with CPU redundancy and an isolated OT network. The Eziwan gateway reads data via OPC-UA from the WinCC server and sends it to a cloud-based analytics platform for predictive maintenance of compressors and heat exchangers. Vibration and temperature data are analyzed using machine learning algorithms to predict failures 72 hours in advance. No modifications to the SCADA system or the existing OT network are required.
Background: Property manager overseeing 50 buildings equipped with energy meters and building automation systems
Each building has an Eziwan gateway that reads energy meters (gas, electricity, water) via Modbus RTU and building management system (BMS) controllers via Modbus TCP. The cloud dashboard consolidates data from all 50 buildings, displaying consumption KPIs, ISO 50001 scores, and deviation alerts. Integration with the property management ERP system via a REST API automates the rebilling of rental charges. An on-premises SCADA system for each building would have been economically unfeasible for this use case.
The 5 Most Common Mistakes in SCADA and IIoT Projects
An industrial SCADA system has been monitoring and controlling critical processes in real time—in some cases for as long as 20 years. Replacing it with a cloud-based IIoT platform in just a few weeks is a serious mistake. The correct approach is an additive one: add IIoT alongside the existing SCADA system, without replacing it, starting with non-critical data.
Exposing SCADA controllers directly to the Internet (without a DMZ or VPN) to allow access to the IIoT platform is a major security flaw. Thousands of industrial SCADA systems are publicly accessible on the Internet. The Eziwan gateway with zero inbound ports is the only connection point between the OT network and the cloud.
Implementing IIoT with proprietary connectors (Siemens S7 MQTT without an OPC-UA server, non-standardized Modbus) creates vendor lock-in. OPC-UA is the interoperable standard that ensures data portability between SCADA, MES, and cloud platforms. Always choose OPC-UA whenever it is available on the equipment.
Proprietary historians (OSIsoft PI, AVEVA Historian) charge per tag (data point). At a site with 10,000 data points, annual licensing costs can easily exceed 50,000 euros. Cloud-based IIoT solutions using InfluxDB or TimescaleDB charge based on the volume of data ingested and stored—resulting in savings of 60 to 80% for new installations without legacy historians.
Adding an IIoT gateway to the SCADA network without physical isolation (dedicated VLAN, firewall between the gateway and SCADA equipment) creates an attack surface. The gateway must be on a dedicated VLAN with access only to the equipment it is supposed to monitor. Eziwan implements this segmentation natively through its selective routing policies.
SCADA, IIoT, or a hybrid solution, depending on your industry?
SCADA remains mandatory for real-time monitoring of treatment processes (chlorination, filtration) and to meet regulatory requirements. Eziwan’s IIoT solution complements this with multi-site monitoring of pumping stations, remote mobile access for staff, and smartphone alerts.
For an industrial SME without an existing SCADA system and without the budget for a full deployment, Eziwan’s cloud-based IIoT solution offers 80% of the functionality at 15% of the cost: equipment monitoring, production tracking, alerts, and remote access. The full SCADA investment can be deferred until a critical size is reached.
Oil and chemical processes with SIL (Safety Integrity Level) require certified SCADA systems with redundancy and strict real-time capabilities. The IIoT complements this with predictive analytics on production data, accessible from remote control centers and field teams.
Building Management Systems (BMS) for monitoring energy consumption, controlling HVAC systems, and managing alarms do not require the real-time response times of a SCADA system. The cloud-based IIoT solution with Eziwan provides all the necessary features with a simpler architecture and lower costs.
Geographically dispersed wind farms and multi-site solar power plants are the ideal use case for the IIoT: centralized monitoring via the cloud, access from anywhere, production analytics, and predictive maintenance. On-premises SCADA systems at each site would be economically unjustified.
SCADA controls and monitors the process in real time; the IIoT collects, logs, and analyzes data on a large scale. When properly designed, the architecture allows them to coexist via a decoupled data bus (OPC UA / MQTT) without affecting the control level.
Functional hierarchy model (levels 0–4): positions SCADA (level 2) and IIoT/MES platforms (levels 3–4) and defines the framework for data exchange.
Standard OT/IT segmentation with an industrial DMZ (level 3.5). The IIoT connects through this DMZ; it never connects directly to the control network.
An object-oriented, secure interoperability standard (X.509 certificates, encryption) with an information model. A preferred bridge between SCADA and IIoT.
A lightweight publish/subscribe protocol, ideal for exception-based reporting over constrained links. Sparkplug B structures the namespace (UNS) for the IIoT.
Automation System Security: Zones and Channels, Segmentation, Access Control — Essential as Soon as the OT Is Connected to the Cloud.
A secondary data channel (monitoring) that runs in parallel with the control channel, without affecting process availability.
The IIoT channel is a secondary read-only data stream, decoupled from the SCADA system. Real-time control remains within the OT; only monitoring data is sent back, filtered and aggregated at the edge.
| Criterion | SCADA | IIoT |
|---|---|---|
| Purpose | Control / Monitoring | Data Collection / Analysis / KPIs |
| Exchange Model | Cyclic Polling | Publish/subscribe (event) |
| Target latency | ms — deterministic | s — best-effort |
| Typical Protocol | Modbus, OPC UA, IEC 104 | MQTT, OPC UA, REST |
| Data Scope | Site / Process | Multi-site / Fleet |
| Availability Criticality | Elevated (process) | Moderate (analytical) |
Golden rule: Never make a control loop dependent on a cloud component. The IIoT observes; it does not control.
Addition of an OPC UA→MQTT bridge in the DMZ, with data transmitted to the cloud for energy KPIs and predictive maintenance; local SCADA system remains unchanged.
Additional Resources on Industrial Monitoring Architectures
Non-intrusive IIoT gateway. Connects to your existing SCADA and PLC systems via OPC-UA or Modbus. Secure remote access, cloud-based dashboard, no changes required to your existing systems.