ISO/TS 20684-4:2022

Overview - ISO/TS 20684-4:2022 (Notifications)

ISO/TS 20684-4:2022 is part of the ISO 20684 series for Intelligent Transport Systems (ITS) and defines how roadside field devices send SNMP-based notifications to one or more managers. The technical specification focuses on real‑time, event-driven messaging from devices such as traffic signals, message signs, weather stations, traffic sensors and roadside C-ITS equipment. It specifies user needs, conformance rules, detailed requirements and the Management Information Base (MIB) design needed to implement standardized SNMP notifications.

Key topics and technical requirements

• Notification concepts: Definitions and roles for key elements - notification aggregator, notification channel, notification factory, notification event and notification packet.
• User needs: Support for monitoring user-defined triggers (defined in ISO/TS 20684-3) to deliver real‑time notifications without continuous polling.
• Data and exchange requirements: How notification contents, timestamps (latency and resolution), maximum packet sizes and event payload limits are represented and exchanged over SNMP.
• Capabilities & configuration: Procedures to determine and configure channel/factory capabilities, retrieve statistics and status, toggle behavior, clear queues and delete channels/factories.
• Aggregation and queuing logic: Rules for aggregating events, queueable vs non‑queueable notifications, and sending aggregated messages to targets.
• Security considerations: High‑level vulnerability guidance and references to secure SNMP practices.
• Conformance & traceability: Conformance clauses, requirement-to-feature mapping and a Requirements Traceability Matrix (Annex B).
• MIB definitions: Normative MIB structures for SNMP implementation (Annex A).

Practical applications and who uses it

ISO/TS 20684-4:2022 is intended for:

• Transport authorities and agencies specifying procurement requirements for roadside ITS equipment.
• Device and firmware manufacturers building SNMP-capable field devices (traffic controllers, sensors, variable message signs).
• System integrators and ITS operators implementing management systems that need consistent, real‑time event notifications.
• Network and operations centers that rely on SNMP for monitoring, incident response and maintenance workflows.

Benefits include reduced polling traffic, faster incident awareness, improved interoperability across vendors, and easier scaling of ITS deployments.

Related standards

• ISO/TS 20684-1:2021 - Overview of the ISO 20684 series and architecture alignment.
• ISO/TS 20684-3 - Trigger definitions used by this part.
• ISO/TS 20684-7 - Support features (e.g., SNMP target parameters).
• NTCIP 1103 - Noted similarities in portions of notification behavior.
• IETF SMIv2 RFCs (2578/2579/2580) - SNMP MIB structure and conformance references.

Keywords: ISO/TS 20684-4:2022, Intelligent Transport Systems, SNMP notifications, roadside modules, ITS field devices, MIB, notification aggregator, notification channel, real-time notifications.