BS ISO 29281 — ITS CALM Non-IP Networking (FNTP) Standard Series

🛣️ BS ISO 29281 is an ISO series on non-IP networking within the Communication Access for Land Mobiles (CALM) framework of intelligent transport systems (ITS), published in the United Kingdom by BSI. The series defines vehicle-to-vehicle and vehicle-to-infrastructure communication protocols that do not rely on the Internet Protocol. Part 1 specifies the Fast Networking & Transport layer Protocol (FNTP), while Part 2 covers Legacy system support. It is a foundational part of the ITS protocol stack that supports low-latency, high-reliability transmission of safety-critical messages. UK participation was coordinated by Technical Committee EPL/278 (Road transport informatics / Intelligent transport systems).

1. Background and Positioning of the Series 📌

CALM is the international ITS communication framework led by ISO TC 204, providing unified access and networking capability for the various wireless media (cellular, DSRC, satellite, infrared) between vehicles and road infrastructure. Within CALM there are both IP-based communications (e.g. ISO 21210 series) and non-IP paths for safety-critical messages. BS ISO 29281 is the core specification for the latter: built on the CALM architecture (ISO 21217), it defines a fast networking protocol that carries applications and transport directly without network-layer IP addressing.

The series supersedes the earlier single-part BS ISO 29281:2011, expanding the content into “protocol specification” and “legacy system support” parts, and introduces Amendment 1 (2014), which replaces Annex A of Part 2. For ITS equipment manufacturers, communication module suppliers and roadside system integrators, conforming to the series means maintaining compatibility with existing CALM devices while gaining deterministic transmission for safety messages.

2. Series Structure and Document List 📋

3. Part 1 — Fast Networking & Transport Layer Protocol (FNTP) 🔧

BS ISO 29281-1:2013 first defines the scope of FNTP: it provides fast, connectionless or connection-oriented data transfer services for upper-layer applications within the CALM architecture. The standard specifies the FNTP architecture and modes of operation, distinguishing operation under different communication scenarios (vehicle-to-vehicle, vehicle-to-infrastructure, infrastructure-to-infrastructure), and defines the structure and encoding of protocol data units. Key characteristics of FNTP include:

• Low overhead: a streamlined header reduces the bytes and latency of safety messages.
• Fast establishment: data exchange can begin without a full handshake, suiting periodic broadcasts of vehicle state messages.
• Multi-media support: it can map onto the different wireless media supported by CALM, enabling unified transmission across heterogeneous networks.
• QoS control: service quality parameters differentiate message priority, ensuring safety-critical messages are delivered first.

The standard also normalises terms and abbreviations and provides conformance statement requirements, forming the basis for testing and certification.

4. Part 2 — Legacy System Support 🔄

BS ISO 29281-2:2013+A1:2014 focuses on how new FNTP-based devices can work with existing CALM devices. The standard defines the requirements for legacy system support, including the interfaces between communication entities in the ITS station architecture, mappings to legacy protocol stacks, and message interoperability mechanisms. Amendment A1 of 2014 replaced Annex A of the standard, further clarifying and updating the related support requirements.

The significance of legacy system support lies in smooth evolution: during large-scale V2X deployment, roads carry many older on-board units and roadside units, and the new protocol must recognise and interoperate with them to avoid communication breaks during the transition. Part 2 provides practical compatibility guidance for this purpose.

5. Engineering and Implementation Practice 🛠️

• 📋 Protocol stack selection: use the FNTP non-IP path for latency-sensitive safety applications, and IP-based CALM communication for large, non-real-time data (such as map updates).
• 🔗 Compatibility verification: before deploying new devices, perform interoperability testing with legacy CALM devices as required by Part 2, confirming no compatibility regression.
• 🧪 Conformance testing: carry out FNTP protocol implementation conformance testing according to Part 1 requirements and issue a statement of conformity to improve device interoperability.
• 🔒 Security mechanisms: protect safety messages using ITS security message authentication (e.g. ISO 16054/21177 series) to prevent forgery and tampering.

6. Frequently Asked Questions ❓