Road vehicles -- Media Oriented Systems Transport (MOST)

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

General Information

Status
Published
Publication Date
25-May-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
21-Apr-2021
Completion Date
21-Apr-2021
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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 21806-14:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 21806-14:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© 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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 21806-14:2021(E)
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

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 21806-14:2021(E)

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
---------------------- Page: 4 ----------------------
ISO 21806-14:2021(E)
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.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 21806-14:2021(E)
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,

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
---------------------- Page: 6 ----------------------
ISO 21806-14:2021(E)

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.
© ISO 2021 – All rights reserved vii
---------------------- Page: 7 ----------------------
ISO 21806-14:2021(E)
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
---------------------- Page: 8 ----------------------
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 2021 – All rights reserved 1
---------------------- Page: 9 ----------------------
ISO 21806-14:2021(E)

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
---------------------- Page: 10 ----------------------
ISO 21806-14:2021(E)
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.

...

INTERNATIONAL ISO
STANDARD 21806-14
First edition
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
PROOF/ÉPREUVE
Reference number
ISO 21806-14:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 21806-14:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© 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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 21806-14:2021(E)
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

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 21806-14:2021(E)

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 ..............................................................................................................................................31

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 ...........................................................................................................................................................34

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 PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 21806-14:2021(E)
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.
© ISO 2021 – All rights reserved PROOF/ÉPREUVE v
---------------------- Page: 5 ----------------------
ISO 21806-14:2021(E)
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,

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 PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 21806-14:2021(E)

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.
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ISO 21806-14:2021(E)
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.
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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.

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ISO 21806-14:2021(E)

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.
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ISO 21806-14:2021(E)
3.12
source drop
detection of unavailability o
...

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