Overview
ISO 21806-14:2021 - "Road vehicles - Media Oriented Systems Transport (MOST) - Part 14: Lean application layer" specifies the technical requirements for a lean application layer for MOST, a synchronous time-division-multiplexing (TDM) in-vehicle network. The standard defines the services and interfaces used to control configuration and behaviour of network management in resource-constrained MOST networks. It covers node types, addressing, data transport, configuration models, network services interfaces, connection management, diagnosis and timing definitions.
Keywords: ISO 21806-14:2021, MOST, Media Oriented Systems Transport, lean application layer, in-vehicle network, network management, node addressing, data transport.
Key topics and technical requirements
- Node kinds and roles: definitions for root node, remote node and listen-only node and their responsibilities in a MOST network.
- Node addressing: rules and formats for assigning and discovering node addresses on the network.
- Data transport and sockets: mechanisms for streaming and network sockets, paths, couplings and how data is moved across the TDM network.
- Network configuration model: network descriptor, node configuration, path and coupling definitions for deterministic behaviour.
- Interfaces:
- NSAI (Network Supervisor / Application Interface) - defines requests, responses and events between applications and the network supervisor.
- LNSI (Lean Network Services Interface) - defines lean network service requests, node discovery, connection management and diagnosis.
- Network management and connection management: procedures for startup/shutdown, node discovery, activating/deactivating paths, monitoring and re-creation of lost paths.
- Diagnosis: support for full- and half-duplex diagnosis and diagnosis using a diagnosis line.
- Timing definitions and timers: timing behaviour and named timers (e.g., t, RD, LNS_Termination) used by the lean application layer.
Practical applications and who uses it
ISO 21806-14 is designed for implementation in MOST-based in-vehicle networks-particularly where a lightweight application layer is required (e.g., infotainment, multimedia distribution, audio/video streaming, and other synchronized data services). Typical users:
- Automotive OEMs and system architects designing in-vehicle networks
- Tier‑1 suppliers implementing MOST interfaces in ECUs and gateways
- Software and firmware engineers implementing NSAI/LNSI and network management
- Test, validation and diagnostic tool vendors creating conformance and troubleshooting tools
- Integration teams responsible for network configuration and lifecycle management
Related standards
- Other parts of the ISO 21806 series that define additional MOST layers and profiles (see ISO 21806 family and MOST technical specifications).
- MOST technology specifications and industry guidelines for physical and transport layers.
ISO 21806-14:2021 provides a focused, interoperable foundation for deterministic, low-overhead network management in MOST TDM environments - enabling consistent node behaviour, reliable connection management and standardized diagnosis across vehicle platforms.