IEC 62541-12:2025 PDF

OPC unified architecture - Part 12: Discovery and global services

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Title (English):

IEC 62541-12:2025

OPC unified architecture - Part 12: Discovery and global services

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 142
Publication date:: December 22, 2025
Edition:: IEC IS 62541 edition 2 version 1
ICS:: 25.040.40

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Description (English):

IEC 62541-12:2025 specifies how OPC Unified Architecture (OPC UA) Clients and Servers interact with DiscoveryServers when used in different scenarios. It specifies the requirements for the LocalDiscoveryServer, LocalDiscoveryServer-ME and GlobalDiscoveryServer. It also defines information models for Certificate management, KeyCredential management and AuthorizationServices. Annex A informatively discusses deployment and configuration aspects. Annex B defines NodeSet and numeric NodeIds. Annex F provides installation rules for the LDS. Annex H compares the Certificate management defined in this document with IETF RFC 7030. This second edition cancels and replaces the first edition published in 2020. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) addition of a "Quantity Model" which can be referenced from EngineeringUnit Properties. The model defines quantities and assigned units. In addition it provides alternative units and the conversion to them; b) addition of rules for ValuePrecision Property: • can also be used for other subtypes like Duration and Decimal. • additional rules when ValuePrecision has negative values.

Technical details

Technical committee: SC 65E - Devices and integration in enterprise systems
SKU: IEC 62541-12:2025

Abstract

Overview

IEC 62541-12:2025 - "OPC Unified Architecture – Part 12: Discovery and global services" (Edition 2.0, 2025) defines how OPC UA Clients and Servers discover one another and interact with discovery infrastructure. The standard specifies requirements and information models for LocalDiscoveryServer, LocalDiscoveryServer‑ME, and GlobalDiscoveryServer, and standardizes Certificate management, KeyCredential management and AuthorizationServices. Informative annexes cover deployment and configuration (Annex A), NodeSet and numeric NodeIds (Annex B), LDS installation rules (Annex F) and a comparison of certificate management with IETF RFC 7030 (Annex H).

Key topics and requirements

Discovery architectures: Covers simple DiscoveryUrl usage, local discovery (multicast/subnet), multicast DNS considerations, global discovery and reverse connection discovery procedures.
Discovery server roles: Requirements and workflows for LocalDiscoveryServer, LocalDiscoveryServer‑ME and GlobalDiscoveryServer including application registration, update and query operations.
Certificate management: Information models and workflows for pull and push certificate management, trust lists, certificate groups and revocation/check processes.
KeyCredential management: Models and services to request, deliver and revoke cryptographic credentials for devices and applications.
AuthorizationServices: Models for requesting access tokens, configuring authorization services and auditing token issuance.
Information models: NodeSets, service types and AuditEvent types for certificate/key/authorization operations; Annex B defines NodeSet and numeric NodeIds.
Security & deployment: Roles, privileges, multicast DNS security considerations and installation rules (Annex F).
Notable technical changes (2025 edition):
- Addition of a Quantity Model for EngineeringUnit properties, alternative units and conversions.
- New rules for ValuePrecision property (applicable to Duration, Decimal and negative-value handling).

Applications and who uses it

Industrial automation vendors implementing OPC UA Servers/Clients and DiscoveryServers.
System integrators building scalable discovery and PKI architectures across OT/IT boundaries.
Device manufacturers adding secure enrollment, key provisioning and remote discovery support.
Network architects & security teams deploying global discovery, reverse connections and certificate lifecycle management.
Software vendors of OPC UA toolkits and IAM solutions integrating AuthorizationServices and access token flows.

Related standards

IEC 62541 series (OPC UA family) - this part complements other parts that define core services, security, information models and transport.
IETF RFC 7030 - compared with the standard’s certificate management in Annex H.

Keywords: OPC UA, DiscoveryServer, LocalDiscoveryServer, GlobalDiscoveryServer, certificate management, key credential, AuthorizationServices, Quantity Model, ValuePrecision.

Related standards

Mentioned in the description and other IEC standards

Abstract

Overview

Key topics and requirements

Discovery architectures: Covers simple DiscoveryUrl usage, local discovery (multicast/subnet), multicast DNS considerations, global discovery and reverse connection discovery procedures.
Discovery server roles: Requirements and workflows for LocalDiscoveryServer, LocalDiscoveryServer‑ME and GlobalDiscoveryServer including application registration, update and query operations.
Certificate management: Information models and workflows for pull and push certificate management, trust lists, certificate groups and revocation/check processes.
KeyCredential management: Models and services to request, deliver and revoke cryptographic credentials for devices and applications.
AuthorizationServices: Models for requesting access tokens, configuring authorization services and auditing token issuance.
Information models: NodeSets, service types and AuditEvent types for certificate/key/authorization operations; Annex B defines NodeSet and numeric NodeIds.
Security & deployment: Roles, privileges, multicast DNS security considerations and installation rules (Annex F).
Notable technical changes (2025 edition):
- Addition of a Quantity Model for EngineeringUnit properties, alternative units and conversions.
- New rules for ValuePrecision property (applicable to Duration, Decimal and negative-value handling).

Applications and who uses it

Industrial automation vendors implementing OPC UA Servers/Clients and DiscoveryServers.
System integrators building scalable discovery and PKI architectures across OT/IT boundaries.
Device manufacturers adding secure enrollment, key provisioning and remote discovery support.
Network architects & security teams deploying global discovery, reverse connections and certificate lifecycle management.
Software vendors of OPC UA toolkits and IAM solutions integrating AuthorizationServices and access token flows.

Related standards

IEC 62541 series (OPC UA family) - this part complements other parts that define core services, security, information models and transport.
IETF RFC 7030 - compared with the standard’s certificate management in Annex H.

Keywords: OPC UA, DiscoveryServer, LocalDiscoveryServer, GlobalDiscoveryServer, certificate management, key credential, AuthorizationServices, Quantity Model, ValuePrecision.

IEC 62541-12:2025 PDF

Technical details

Abstract

Overview

Key topics and requirements

Applications and who uses it

Related standards

Related standards

Abstract

Overview

Key topics and requirements

Applications and who uses it

Related standards

Related standards

OPC unified architecture - Part 2: Security Model (IEC 62541-2:2026)

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