What is ISO 21806‑6 about?
ISO 21806‑6 is part six of the multi-series standard that specifies technical requirements related to the MOST data link layer functionality.
A MOST network is comprised of two or more nodes connected through a physical layer. The data link layer functionality is provided by each node. On each network, all nodes are synchronised, and one node provides the system clock. This node is the TimingMaster, while all other nodes are TimingSlaves. The timing configuration of the node (TimingMaster or TimingSlave) determines the tasks that need to be performed on the data link layer.
The data link layer specifies the following subjects:
- The service interface to the network layer
- The network frame, its areas and indicators
- The different network channels
- The different flow control mechanisms
- The load-adaptive arbitration and the round-robin arbitration
- The different addressing options
- The different cyclic redundancy checks, their usage and the crc acknowledge
- The frame indicators
Who is ISO 21806‑6 for?
ISO 21806‑6 on Media Oriented Systems Transport (MOST) data link layer is useful for:
- Vehicle manufacturers
- Car infotainment manufacturers and developers
- Vehicle data services providers
- Developers of multimedia and infotainment systems
Why should you use ISO 21806‑6?
MOST enable the transport of high-quality service (QoS) audio and video together with packet data and real-time control to support modern automotive multimedia and similar applications. MOST is a function-oriented communication technology to network a variety of multimedia devices comprising one or more MOST nodes.
ISO 21806‑6 series helps you implement the MOST communication technology into multimedia devices and to provide conformance test plans for implementing related test tools and test procedures.
ISO 21806‑6 provides an overview of data link layer service interface to upper layers. The DLL service interface defines the abstract interface to the OSI transport layer and network layer.
ISO 21806‑6 provides an overview of the parameters that are used in the specified service interface and passed from TL/NL to DLL.
The allocation channel is used to allocate or de-allocate bandwidth in the source data area.
Whenever a node intends to make use of network frame bytes in the source data area, it allocates those bytes in an allocation request. An arbitration mechanism allows getting access to bytes that are not yet in use. The allocation channel consists of two consecutive bytes of the network frame. These two bytes together transport the allocation word. ISO 21806‑6 specifies the allocation word general format.
ISO 21806‑6 lays out guidelines for error handling.
