Gateways are necessary to translate communication between PLC systems using industrial protocols and modern IT management infrastructures, introducing operational challenges that automation professionals must face. Gateway-dependent systems can introduce latency, create potential failure points, and complicate system architecture.

Network infrastructure issues can cause random occurrences of “lost communication” interlocks which stop the operation of entire systems. Prioritizing PLC traffic through traditional networking approaches often fails to resolve these issues, requiring dedicated infrastructure solutions to ensure reliable communication.

Redfish represents a paradigm shift in data center management, establishing a universal communication protocol that addresses the fragmentation caused by multiple incompatible standards. Redfish is a standard designed to deliver simple and secure management for converged, hybrid IT and Software Defined Data Centers (SDDC), leveraging common Internet and web services standards to expose information directly to modern tool chains. The protocol uses RESTful interface semantics and JSON data format, making it both human-readable and machine-capable.

The strategic importance of Redfish lies in its ability to eliminate vendor lock-in and increase system administrator productivity. Multiple incompatible standards, protocols, and tools require significant expertise to use and do not scale to modern environments, while Redfish enables the management of compute, network, storage and facilities equipment using the same simple interface. This standardization provides output usable by machines and humans alike, enabling flexible and scalable end-to-end interoperability for converged, hybrid IT.

Redfish comprehensively supports data center cooling infrastructure through specialized thermal equipment schemas. The DMTF has developed comprehensive Redfish schemas specifically for thermal equipment management, with the Redfish 2023.1 release introducing broad support for liquid cooling equipment, including Coolant Distribution Units (CDUs), rear-door heat exchangers, immersion cooling systems, and server connections. These schemas provide detailed modeling of cooling subsystems including filters, pumps, reservoirs, manifolds, and leak detection systems.

The protocol enables management of cooling loops at multiple levels, from facility-wide primary cooling systems to rack-level secondary loops. Redfish thermal equipment schemas support modeling of cooling loop connections, coolant connectors, and the relationships between different cooling equipment components. This comprehensive approach allows for coordinated control of coolant flow, temperature readings, and system status across the entire cooling infrastructure.

Redfish-embedded PLCs eliminate the complexity and reliability issues associated with gateway-dependent communication systems. Such advanced controllers can exchange data directly in real-time with data center IT management systems via Redfish without requiring gateways or protocol translation. This direct integration enables real-time data exchange between PLCs and data center management systems without protocol translation overhead.

The operational benefits of direct Redfish integration include simplified architecture, reduced latency, improved reliability, and streamlined management. Redfish-embedded PLCs can simultaneously handle common automation tasks, control complex cooling loops, and communicate with infrastructure components using the universal Redfish protocol. This integration capability was previously only available for large-scale IT hardware.

Redfish-embedded PLCs provide sophisticated control capabilities across all major data center cooling technologies. The different types of cooling loops that these systems can control include:

Air-Based Cooling Systems: Traditional CRAC (Computer Room Air Conditioning) units and CRAH (Computer Room Air Handlers) that are commonly used in smaller centers and older systems. These systems rely on precise fan speed control and temperature regulation to maintain optimal environmental conditions.

Direct Liquid Cooling (DLC): Advanced systems where liquid coolant is circulated directly through server racks, providing superior cooling efficiency compared to air-based systems[10][8]. Direct-to-chip liquid cooling involves the direct application of liquid coolants to processors and other critical components, achieving more efficient heat transfer than air cooling.

Liquid Immersion Cooling: Systems where servers are submerged in dielectric liquids, representing the most advanced cooling technology for high-density applications. This method involves submerging server components in dielectric coolants such as mineral oil, providing highly energy-efficient cooling[.

Hybrid Cooling Systems: Combined approaches that utilize both air and liquid cooling technologies to optimize energy efficiency and cooling performance based on environmental conditions and load requirements.

Redfish-embedded PLCs enable seamless integration with environmental sensors and cooling equipment throughout the data center. These systems can access sensor data via the Redfish API to determine current thermal conditions within the data center, including temperature, humidity, and airflow rates. The PLCs can then use this comprehensive environmental data to make informed control decisions across the entire facility.

Remote management capabilities represent another significant advantage, as PLCs can remotely control cooling equipment via Redfish for real-time adjustments. This includes commands to adjust airflow, activate cooling zones, or change the power state of cooling equipment. The ability to receive HTTP GET requests to Redfish endpoints and respond with JSON payloads containing thermal information enables seamless integration with existing data center management tools.

Unitronics is currently the only manufacturer offering PLCs with native Redfish support, representing a unique position in the rapidly growing data center automation market. Their UniStream Built-in series controllers can exchange data directly in real-time with data center IT management systems via Redfish without requiring gateways. This functionality provides automation professionals with access to cutting-edge technology that addresses the evolving needs of modern data center cooling management.