ISO 21806-14:2021

Road vehicles - Media Oriented Systems Transport (MOST) - Part 14: Lean application layer

This document specifies the technical requirements for the lean application layer for MOST, a synchronous time-division-multiplexing network. The lean application layer includes a specification of the services available to control the configuration and behaviour of the network management. The lean application layer covers the definition of: - node kinds, - node addressing, - data transport, - network configuration, - lean network services interface, - network management, including connection management, - diagnosis, and - timing definitions.

Véhicules routiers — Système de transport axé sur les médias — Partie 14: Couche d'application allégée

General Information

• Status: Published
• Publication Date: 25-May-2021
• ICS: 43.040.15 - Car informatics. On board computer systems
• Technical Committee: ISO/TC 22/SC 31 - Data communication
• Drafting Committee: ISO/TC 22/SC 31/WG 3 - In-vehicle networks
• Current Stage: 6060 - International Standard published
• Start Date: 26-May-2021
• Due Date: 21-May-2022
• Completion Date: 26-May-2021

Relations

• Consolidated By: ISO 20701:2024 - Leather - Tests for colour fastness - Colour fastness to saliva
• Effective Date: 22-Apr-2023

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.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21806-14
First edition
2021-05
Road vehicles — Media Oriented
Systems Transport (MOST) —
Part 14:
Lean application layer
Véhicules routiers — Système de transport axé sur les médias —
Partie 14: Couche d'application allégée
Reference number
©
ISO 2021
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
4.1 Symbols . 3
4.2 Abbreviated terms . 3
5 Conventions . 3
6 Basic principles . 3
7 Node kinds . 4
7.1 General . 4
7.2 Root node . 4
7.2.1 General. 4
7.2.2 Lean network services . 5
7.2.3 Network descriptor . 5
7.3 Remote node . 6
7.4 Listen-only node . 6
8 Node addressing . 6
9 Data transport . 7
10 Network configuration . 7
10.1 General . 7
10.2 Network . 7
10.3 Node . 8
10.4 Path . 8
10.5 Coupling . 8
10.6 Streaming socket . 9
10.7 Network socket . 9
11 Network supervisor/application interface (NSAI) .10
11.1 Overview .10
11.2 Requests, responses, and events .11
11.2.1 Network startup and shutdown .11
11.2.2 Connection management .11
11.2.3 Diagnosis .11
12 Lean network services interface (LNSI) .12
12.1 Overview .12
12.2 Requests, responses, and events .14
12.2.1 Lean network services .14
12.2.2 Network startup and shutdown .14
12.2.3 Node discovery .14
12.2.4 Connection management .15
12.2.5 Diagnosis .15
13 Network management .15
13.1 Network startup and shutdown .15
13.2 Network events .15
13.2.1 General.15
13.2.2 End of network activity .16
13.2.3 Unlock and critical unlock .16
13.2.4 Network change event .16
13.2.5 Source drop .16
13.3 Node discovery .16
13.3.1 General.16
13.3.2 Addresses .17
13.3.3 Scanning the network .17
13.3.4 Adding nodes to the network .18
13.3.5 Reset detection .21
13.4 Connection management .23
13.4.1 General.23
13.4.2 Sockets .24
13.4.3 Couplings .24
13.4.4 Paths .25
13.4.5 Activating paths .25
13.4.6 Deactivating paths .26
13.4.7 Re-creation of lost paths .27
13.4.8 Monitoring .27
13.5 Network management message format .27
13.5.1 General.27
13.5.2 Command and report reference .27
13.5.3 Message IDs for commands and reports .30
14 Diagnosis .31
14.1 General .31
14.2 Full-duplex network diagnosis .31
14.3 Half-duplex network diagnosis .32
14.4 Network diagnosis using diagnosis line .32
15 Timing definitions .33
15.1 Overview .33
15.2 Timer t .
Hello 34
15.2.1 Purpose .34
15.2.2 Start and stop conditions.34
15.2.3 Timer expiration .34
15.3 Timer t .
RD 34
15.3.1 Purpose .34
15.3.2 Start and stop conditions.34
15.3.3 Timer expiration .35
15.4 Timer t .
LNS_Termination 35
15.4.1 Purpose .35
15.4.2 Start and stop conditions.35
15.4.3 Timer expiration .35
16 Service interface definition to transport layer and network layer .35
Annex A (normative) Parameters for LNSI and network management messages .36
Annex B (informative) XSD for validation of XML .43
Annex C (informative) Network descriptor example .53
Bibliography .55
iv © ISO 2021 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 31,
Data communication.
A list of all parts in the ISO 21806 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
The Media Oriented Systems Transport (MOST) communication technology was initially developed at
the end of the 1990s in order to support complex audio applications in cars. The MOST Cooperation was
founded in 1998 with the goal to develop and enable the technology for the automotive industry. Today,
1)
MOST enables the transport of high quality of 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.
Figure 1 shows a MOST network example.
Figure 1 — MOST network example
The MOST communication technology provides:
— synchronous and isochronous streaming,
— small overhead for administrative communication control,
— a functional and hierarchical system model,
— API standardization through a function block (FBlock) framework,
— free partitioning of functionality to real devices,
— service discovery and notification, and
[2]
— flexibly scalable automotive-ready Ethernet communication according to ISO/IEC/IEEE 8802-3 .
MOST is a synchronous time-division-multiplexing (TDM) network that transports different data types
on separate channels at low latency. MOST supports different bit rates and physical layers. The network
clock is provided with a continuous data signal.
1) MOST® is the registered trademark of Microchip Technology Inc. This information is given for the convenience
of users of this document and does not constitute an endorsement by ISO.
vi © ISO 2021 – All rights reserved

Within the synchronous base data signal, the content of multiple streaming connections and control
data is transported. For streaming data connections, bandwidth is reserved to avoid interruptions,
collisions, or delays in the transport of the data stream.
MOST specifies mechanisms for sending anisochronous, packet-based data in addition to control data
and streaming data. The transmission of packet-based data is separated from the transmission of
control data and streaming data. None of them interfere with each other.
A MOST network consists of devices that are connected to one common control channel and packet
channel.
In summary, MOST is a network that has mechanisms to transport the various signals and data streams
that occur in multimedia and infotainment systems.
The ISO standards maintenance portal (https:// standards .iso .org/ iso/ ) provides references to MOST
specifications implemented in today's road vehicles because easy access via hyperlinks to these
specifications is necessary. It references documents that are normative or informative for the MOST
versions 4V0, 3V1, 3V0, and 2V5.
The ISO 21806 series has been established in order to specify requirements and recommendations
for implementing the MOST communication technology into multimedia devices and to provide
conformance test plans for implementing related test tools and test procedures.
To achieve this, the ISO 21806 series is based on the open systems interconnection (OSI) basic reference
[1] [3]
model in accordance with ISO/IEC 7498-1 and ISO/IEC 10731, which structures communication
systems into seven layers as shown in Figure 2. Stream transmission applications use a direct stream
data interface (transparent) to the data link layer.
Figure 2 — The ISO 21806 series reference according to the OSI model
The International Organization for Standardization (ISO) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent.
ISO takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In
this respect, the statement of the holder of this patent right is registered with ISO. Information may be
obtained from the patent database available at www .iso .org/ patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those in the patent database. ISO shall not be held responsible for identifying
any or all such patent rights.
viii © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 21806-14:2021(E)
Road vehicles — Media Oriented Systems Transport
(MOST) —
Part 14:
Lean application layer
1 Scope
This document specifies the technical requirements for the lean application layer for MOST, a
synchronous time-division-multiplexing network.
The lean application layer includes a specification of the services available to control the configuration
and behaviour of the network management.
The lean application layer covers the definition of:
— node kinds,
— node addressing,
— data transport,
— network configuration,
— lean network services interface,
— network management, including connection management,
— diagnosis, and
— timing definitions.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 21806-1, Road vehicles — Media Oriented Systems Transport (MOST) — Part 1: General information
and definitions
ISO 21806-4, Road vehicles — Media Oriented Systems Transport (MOST) — Part 4: Transport layer and
network layer
ISO 21806-10, Road vehicles — Media Oriented Systems Transport (MOST) — Part 10: 150-Mbit/s coaxial
physical layer
ISO 21806-12, Road vehicles — Media Oriented Systems Transport (MOST) — Part 12: 50-Mbit/s balanced
media physical layer
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21806-1 and the following
apply.
ISO and IEC maintain terminological databases for use in standardisation at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
coupling
tie between a streaming socket (3.11) and a network socket
3.2
lean network service
implementation of a software library that provides mechanisms to support node discovery (3.6) and
establish a network configuration (3.3)
3.3
network configuration
nodes currently connected to the network and paths (3.7) established for transmission
3.4
network descriptor
list of nodes allowed to participate in network communication, including valid paths (3.7) with
definition of couplings (3.1) and streaming connections
3.5
network supervisor
entity that is responsible for monitoring the network configuration (3.3)
3.6
node discovery
determination of the presence of the expected remote nodes (3.8)
3.7
path
two couplings (3.1) and a streaming connection
3.8
remote node
node that participates in a MOST network that conforms to this document and does not implement the
lean network services (3.2)
3.9
root node
node in a MOST network that controls the network (discover, configure, and connect)
3.10
signature
unique identification of a node
Note 1 to entry: The signature includes the logical node address, DiagID, MAC address, etc. It is provided at design
time. The signature is matched against the information contained in the network descriptor (3.4).
3.11
socket
interface of the MNC
Note 1 to entry: A socket is either a streaming socket or a network socket.
2 © ISO 2021 – All rights reserved

3.12
source drop
detection of unavailability of a streaming connection by a sink
Note 1 to entry: This could, for example, be caused by network or source malfunction.
4 Symbols and abbreviated terms
4.1 Symbols
--- empty table cell or feature undefined
4.2 Abbreviated terms
LNSI lean network services interface
NSAI network supervisor/application interface
5 Conventions
[2]
This document is based on OSI service conventions as specified in ISO/IEC 10731 .
6 Basic principles
The MOST network consists of nodes. The node that provides the network clock and is responsible for
startup and shutdown of the network, as well as network management is called root node. The other
nodes that participate in the network communication are called remote nodes.
Figure 3 shows the MOST network example.
Figure 3 — MOST network example
Network management includes the process for startup and shutdown of the network.
Node discovery is a network management process that identifies all nodes in the network, which
present a unique signature to the root node. Node discovery determines the presence of the expected
remote nodes.
The nodes that currently exist in the network and the streaming connections between those nodes are
called network configuration. The network supervisor in the root node is responsible for monitoring
the network configuration.
The lean network services implement a software library that provides the root node with mechanisms
for node discovery and establishing a network configuration. A remote node reacts to any lean network
services request, for example, it answers to Hello_Get commands.
The connection management, as part of the lean network services, is a process that establishes paths,
couplings, connections, and sockets based on the network descriptor.
7 Node kinds
7.1 General
REQ 7.1 AL – Root node and remote nodes
There shall be one root node and up to 63 remote nodes.
The maximum number of nodes may be further reduced by physical layer restrictions.
7.2 Root node
7.2.1 General
The root node in a MOST network controls the network (discover, configure, and connect). This node is
the one that implements the mandatory network supervisor.
REQ 7.2 AL – Root node is TimingMaster
The root node shall be the TimingMaster.

REQ 7.3 AL – Root node structure
The root node shall contain:
— the network supervisor, and
— the lean network services.
Figure 4 shows the root node. The application consists of software and/or hardware. It uses the network
supervisor/application interface (NSAI) to communicate with the network supervisor. The application
exchanges streaming data and packet data with the MNC.
The network supervisor uses the network descriptor to configure the lean network services by means
of the lean network services interface (LNSI). The LNSI, in one direction, transports requests from the
network supervisor to the lean network services and, in the opposite direction, provides responses to
the network supervisor.
The lean network services exchange network management messages with the MNC. The lean network
services send commands to and receive reports from the MNC.
The MNC of the root node is the TimingMaster of the MOST network.
4 © ISO 2021 – All rights reserved

Figure 4 — Root node
7.2.2 Lean network services
The lean network services are implemented in the root node, exclusively.
REQ 7.4 AL – Lean network services scope
The lean network services shall implement:
— startup;
— shutdown;
— node discovery;
— connection management; and
— diagnostic functions.
7.2.3 Network descriptor
REQ 7.5 AL – Network descriptor
The network descriptor shall contain the definition of:
— nodes allowed to participate in network communication;
— valid paths;
— couplings;
— streaming connections;
— network sockets; and
— streaming sockets.
NOTE  The network descriptor is static and known a priori.
REQ 7.6 AL – Network supervisor relies on network descriptor
Based on the network descriptor, the network supervisor shall determine which nodes are permitted to join
the MOST network.
An example of a network descriptor is provided in Annex C. The status of Annex C is informative.
7.3 Remote node
REQ 7.7 AL – Remote node structure
A remote node shall not contain the network supervisor or the lean network services.
Network management and connection management are provided by the MNC.
REQ 7.8 AL – Remote node reacts on requests
The MNC of a remote node shall answer lean network service requests.
Figure 5 specifies the remote node. The application consists of software and/or hardware. It exchanges
streaming data and packet data with the MNC.
Figure 5 — Remote node
7.4 Listen-only node
For network analysis purposes, a certain node kind exists that does not change the content of network
frames. A listen-only node is invisible to other nodes.
8 Node addressing
REQ 7.9 AL – 16-bit address area structure
For 16-bit addressing, the address area of an MNC shall be structured as specified in Table 1.
6 © ISO 2021 – All rights reserved

Table 1 — 16-bit Address range
Address range Description
0000 to 000F Address range for internal communication between local network controller and lean
16 16
network services
0010 to 02FF Logical node address range
16 16
0300 to 03C7 Group address range
16 16
03C8
Blocking broadcast address
03C9 to 03FE Group address range
16 16
03FF
Non-blocking broadcast address
0400 to 043F Node position address range
16 16
0440 to 04FF Reserved
16 16
0500 to 0EFF Logical node address range
16 16
0F00 to 0FEF Address range for administrative purposes
16 16
0FF0
Debug address
0FF1 to 0FFD Address range for administrative purposes
16 16
0FFE
Un-initialised logical node address
0FFF
Address for administrative purposes
1000 to FFFF Reserved
16 16
9 Data transport
The application may use the packet channel for communication with network devices. The application
should not use the control channel.
REQ 7.10 AL – Administrative communication
The control channel shall be used for administrative communication, that is, network management and con-
nection management.
10 Network configuration
10.1 General
The network descriptor determines the network configuration, the nodes and the streaming
connections between them. It can be either edited text-based or by use of a graphical tool.
The network descriptor is used to generate a data definition in a format that the lean network services
are capable of processing.
The tables in the following subclauses contain a column that is titled "stored". The entries marked
with "yes" are contained in the storage format for the network descriptor, while the entries marked
with "no" are relevant for the network configuration, which is established during runtime. "Optional"
entries, mainly resource handles, are relevant during runtime but may also be pre-configured.
10.2 Network
REQ 7.11 AL – Network configuration properties for the network
The properties of the network configuration that are specified in Table 2 shall be associated with the network.
Table 2 — Network properties
Property Data type/values Stored Description
Activation enumeration {on, off}
no Activation determines the intended
state of the network.
10.3 Node
REQ 7.12 AL – Network configuration properties for nodes
The properties of the network configuration that are specified in Table 3 shall be associated with nodes.
Table 3 — Node properties
Property Data type/values Stored Description
Availability enumeration {available, not_
no The availability of a node depends
available}
on whether the Hello/Welcome
sequence is performed successfully.
Signature complexType {NodeAddress,
yes The signature of a node contains
GroupAddress, MACAddress_47to32,
the DiagID and other relevant
MACAddress_31to16,
information.
MACAddress_15to0, DiagID,
NumberOfPorts}
10.4 Path
Paths are links between two nodes, consisting of two couplings and a streaming connection.
REQ 7.13 AL – Network configuration properties for paths
Table 4 specifies the properties of the network configuration for paths.
Table 4 — Path properties
Property Data type/values Stored Description
Activation enumeration {on,
optional Activation triggers the creation of the path.
off}
Identifier string
yes Identifier is the unique identifier of the path.
In_Coupling string
yes In_Coupling is the identifier of the coupling that
forwards the data from the network socket to the
streaming socket.
Out_Coupling string
yes Out_Coupling is the identifier of the coupling that
forwards the data from the streaming socket to the
network socket.
10.5 Coupling
A coupling is a tie between a streaming socket and a network socket.
REQ 7.14 AL – In_Coupling direction
The Direction of both sockets for an In_Coupling shall be in.

REQ 7.15 AL – Out_Coupling direction
The Direction of both sockets for an Out_Coupling shall be out.
8 © ISO 2021 – All rights reserved

REQ 7.16 AL – Network configuration properties for couplings
The properties of the network configuration specified in Table 5 shall be associated with couplings.
Table 5 — Coupling properties
Property Data type/values Stored Description
Direction enumeration {in,
yes Determines whether the coupling is an In_
out}
Coupling or an Out_Coupling.
Identifier string
yes Identifier is the unique identifier of the cou-
pling.
Usage_Counter unsignedByte
no A coupling can be used in more than one path.
The usage counter reflects how many paths in-
clude the coupling.
Network_Socket string
yes Network_Socket is the identifier of the network
socket.
Node string
yes Node is the unique identifier of the associated
node.
ResourceHandle unsignedShort
optional Handle of the coupling, which is unique within a
node. FFFF indicates an invalid value.
Streaming_Socket string
yes Streaming_Socket is the identifier of the
streaming socket.
10.6 Streaming socket
REQ 7.17 AL – Network configuration properties for streaming sockets
The properties of the network configuration specified in Table 6 shall be associated with streaming sockets.
Additional vendor-specific properties may exist.
Table 6 — Streaming socket properties
Property Data type/values Stored Description
Direction enumeration {in,
yes Determines whether the streaming socket is used in
out}
in- or out-direction.
Identifier string
yes Identifier is the unique identifier of the stream-
ing socket.
ResourceHandle unsignedShort
optional Handle of the streaming socket, which is unique
within a node. FFFF indicates an invalid value.
10.7 Network socket
REQ 7.18 AL – Network configuration properties for network sockets
The properties of the network configuration specified in Table 7 shall be associated with network sockets.
Table 7 — Network socket properties
Property Data type/values Stored Description
Bandwidth unsignedShort
yes It is the bandwidth of the streaming connection.
Channel enumeration
yes Determines whether the synchronous channel or
{synchronous,
the isochronous channel is used.
isochronous}
Table 7 (continued)
Property Data type/values Stored Description
Connection_Label unsignedShort
optional Connection_Label is the MOST connection label
that is associated with the network socket.
Direction enumeration {in,
yes Determines whether the network socket is used
out}
in in- or out-direction.
Identifier string
yes Identifier is the unique identifier of the net-
work socket.
ResourceHandle unsignedShort
optional Handle of the network socket, which is unique
within a node. FFFF indicates an invalid value.
11 Network supervisor/application interface (NSAI)
11.1 Overview
The network supervisor/application interface (NSAI) provides access to the network supervisor.
REQ 7.19 AL – NSAI requests, responses, and events
The requests, responses, and events that are exchanged between the application and the network supervisor
shall be in accordance with Tables 8, 9, and 10.
Requests are directed from the application to the network supervisor. Each request is answered by a
response. Events are sent from the lean network services to the network supervisor. The parameters
are specified in Annex A and shall be followed. The status of Annex A is normative.
In general, the network supervisor decides what actions are taken if it receives a response with
Status = error.
Table 8 — Messages for the NSAI – Network startup and shutdown
Message Parameter Description
Network_Startup_Request BoundaryDescriptor
Request to start up the MOST network
Network_Startup_Response Status
Response to the network startup
request
Network_Shutdown_Request ---
Request to shut down the MOST net-
work
Network_Shutdown_Response Status
Response to the shutdown request
Network_Status_Event Accessibility,
Indication of a network status change
AccessibilityInfo,
TransitionCause,
NodeAddress,
VisibleNodes,
PacketBandwidth
Table 9 — Messages for the NSAI – Connection management
Message Parameter Description
Connection_Management_Start_Request NetworkDescriptor
Request to start connec-
tion management
Connection_Management_Start_Response Status
Response to connec-
tion management start
request
Connection_Management_Stop_Request ---
Request to stop connec-
tion management
10 © ISO 2021 – All rights reserved

Table 9 (continued)
Message Parameter Description
Connection_Management_Stop_Response Status
Response to connec-
tion management stop
request
Path_Activation_Set_Request Path, Activation
Request to set the
Activation of a path
Path_Activation_Set_Response Path, Activation,
Response to path
Status
Activation set request
Table 10 — Messages for the NSAI – Diagnosis
Message Parameter Description
Diagnosis_Start_Request DiagnosisSelector
Request to start diagnosis
Diagnosis_Start_Response DiagnosisSelector,
Response to diagnosis start request
Status
Diagnosis_Result_Event DiagResult
Result for one link or node during
diagnosis
Diagnosis_End_Event ---
Indication of completion of the diagno-
sis process
11.2 Requests, responses, and events
11.2.1 Network startup and shutdown
The application uses Network_Startup_Request to start up the MOST network. In Network_Startup_
Response, if Status indicates success, the network is active. The value error indicates failure during
startup.
The application uses Network_Shutdown_Request to shut down the MOST network. In Network_
Shutdown_Response, if Status indicates success, the network is shut down. The value error in
...