ISO 21806-4:2020

INTERNATIONAL ISO
STANDARD 21806-4
First edition
2020-09
Road vehicles — Media Oriented
Systems Transport (MOST) —
Part 4:
Transport layer and network layer
Véhicules routiers — Système de transport axé sur les médias —
Partie 4: Couche de transport et couche réseau
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – 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 . 2
4.1 Symbols . 2
4.2 Abbreviated terms . 2
5 Conventions . 2
6 Transport layer service interface to upper OSI layers . 3
6.1 Overview of services . 3
6.2 Data type definitions . 3
6.3 Parameters . 4
6.3.1 Parameters — NL/TL to upper layers . 4
6.3.2 Parameters — Upper layers to TL/NL . 7
6.3.3 Parameters – NL/TL to upper layers and upper layers to TL/NL .10
6.4 Event indications and action requests .12
6.4.1 N_EVENT.INDICATE .12
6.4.2 N_NODE_POSITION.INDICATE .12
6.4.3 N_MAXIMUM_NODE_POSITION.INDICATE .12
6.4.4 N_NET_INTERFACE_TRANSITION.INDICATE .12
6.4.5 N_DIAGRESULT.INDICATE .13
6.4.6 N_SHUTDOWN_REASON.INDICATE .13
6.4.7 N_ACTION.REQUEST .13
6.4.8 N_NETWORK_STARTUP.REQUEST .13
6.4.9 N_SET_GROUP_ADDRESS.REQUEST .14
6.4.10 N_SET_NODE_ADDRESS.REQUEST .14
6.4.11 N_SET_EUI_48.REQUEST .14
6.5 Control data .14
6.5.1 N_CONTROL_DATA.RECEIVE .14
6.5.2 N_CONTROL_DATA.CONFIRM .15
6.5.3 N_SET_MESSAGE_ATTRIBUTES.REQUEST .15
6.5.4 N_CONTROL_DATA.SEND .15
6.6 Packet data .15
6.6.1 16-bit addressing.15
6.6.2 48-bit addressing.16
6.7 Streaming data .16
6.7.1 N_ALLOCATE.INDICATE.16
6.7.2 N_DEALLOCATE.INDICATE .17
6.7.3 N_CONNECT.INDICATE .17
6.7.4 N_DISCONNECT.INDICATE .17
6.7.5 N_SOURCE_DROP.INDICATE .17
6.7.6 N_STREAMING_DATA.RECEIVE .18
6.7.7 N_ALLOCATE.REQUEST .18
6.7.8 N_DEALLOCATE.REQUEST .18
6.7.9 N_CONNECT.REQUEST .18
6.7.10 N_DISCONNECT.REQUEST .19
6.7.11 N_STREAMING_DATA.SEND.19
7 TL — Transport layer .19
7.1 TL — Overview .19
7.2 TL — Data transport mechanism .19
7.2.1 TL — Transport service .19
7.2.2 TL — Service for control data .19
7.2.3 TL — Service for source data .24
8 NL — Network layer.25
8.1 NL — Overview.25
8.2 NL — Services .25
8.2.1 NL — States and state transitions .25
8.2.2 NL — Network error detection and management .34
8.3 NL — Timing .39
8.3.1 NL — General .39
8.3.2 NL — Timers .39
8.3.3 NL — Timing constraints .39
8.3.4 NL — Network startup and changes .40
8.3.5 NL — Network shutdown .43
8.3.6 NL — General communication .46
8.4 NL — Data link layer service interface .46
Annex A (informative) Ring break diagnosis (RBD) .47
Bibliography .56
iv © ISO 2020 – 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
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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
[6]
— 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 2020 – 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] [4]
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 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 21806-4:2020(E)
Road vehicles — Media Oriented Systems Transport
(MOST) —
Part 4:
Transport layer and network layer
1 Scope
This document specifies technical requirements related to the MOST transport layer and network layer
functionality:
— the service interface to application layer;
— the network layer services;
— the data transport mechanism;
— the dynamic behaviour of a node;
— the network error management.
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
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 standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
active TimingSlave
TimingSlave that initiates a network startup (3.2)
3.2
network startup
network activity that commences so that all nodes in the MOST network change to s_NetInterface_
Normal_Operation
3.3
network wake-up
process of all nodes in the MOST network exiting s_NetInterface_Sleep
3.4
network wake-up event
network activity or electrical wake-up line activity
3.5
passive TimingSlave
node that participates in a network startup (3.2), not initiating it
3.6
qualified local wake-up event
local trigger (one that does not affect all devices) that causes exiting s_NetInterface_Sleep
3.7
wake-up event
trigger for exiting s_NetInterface_Sleep
4 Symbols and abbreviated terms
4.1 Symbols
--- empty cell/undefined
L maximum payload length for AMS
AMSmax
L maximum payload length for control data
CMmax
4.2 Abbreviated terms
A: action
AMS application message service
C: condition
ev_
prefix event name
MsgID
message identifier
NL network layer
RBD ring break diagnosis
s_
prefix state name
SegCnt
segment counter
TelID
telegram identifier
TelLen
telegram length
TL transport layer
5 Conventions
[4]
This document is based on OSI service conventions as specified in ISO/IEC 10731 .
2 © ISO 2020 – All rights reserved

6 Transport layer service interface to upper OSI layers
6.1 Overview of services
Figure 3 shows the transport layer (TL) service interface, which specifies the interface to the upper OSI
[1]
layers, see ISO 21806-2 .
Figure 3 — Service interface to upper OSI layers
6.2 Data type definitions
REQ 4.1 Service interface – Data type definitions
The data types shall be in accordance to:
— Enum: 8-bit enumeration;
— Unsigned Byte: 8-bit unsigned numeric value;
— Unsigned Word: 16-bit unsigned numeric value;
— Unsigned Long: 32-bit unsigned numeric value;
— EUI-48: 48-bit address value;
— Byte Array: sequence of 8-bit aligned data.
6.3 Parameters
6.3.1 Parameters — NL/TL to upper layers
6.3.1.1 Overview
Table 1 specifies the parameters that are used in the service interface and passed from NL/TL to
upper layers.
Table 1 — Parameters passed from NL/TL to upper layers
Parameter Data type Description
Application_Event
Enum { An event that is reported to
Unlock, the application.
Stable_Lock,
Lock_Flag,
Network_Change_Event,
Shutdown_Flag,
MOST_Output_Off,
Network_Activity
}
NetInterface_Transition
Enum { A transition between
ev_Wake_Up, NetInterface states
ev_Sleep,
ev_Start_Up,
ev_Diagnosis_Start,
ev_Init_Error_Shutdown,
ev_Init_Diagnosis_Start,
ev_Init_Ready,
ev_Error_Shutdown,
ev_Normal_Shutdown,
ev_Diagnosis_Ready,
ev_Diagnosis_End
}
DiagResult
Enum { DiagResult of the ring break
No_Error, diagnosis
Ring_Break,
Weak_Signal,
Diagnosis_Inconclusive
}
Relative_Position Unsigned Byte
Relative position of a node to a
ring break
Shutdown_Reason
Enum { Shutdown reason
No_Result_Available,
No_Fault_Saved,
Sudden_Signal_Off,
Critical_Unlock
}
Node_Position Unsigned Byte
Position of the node
Maximum_Position Unsigned Byte
Maximum position information
Transmission_Status
Enum { Transmission status that is
Success, reported back to the sender.
Buffer_Full,
CRC_Error,
Wrong_Target
}
4 © ISO 2020 – All rights reserved

6.3.1.2 Application_Event
Application_Event corresponds to events that are used to notify the application about changes in lower
layers, which require no additional information.
REQ 4.2 Service interface – Parameters – NL/TL to upper layers – Application_Event
The Application_Event parameter shall be of data type Enum and shall contain the value specified according
to Table 2.
Table 2 — Application_Event values
Enum value Description
Unlock
Unlock event occurred.
Stable_Lock
Stable lock reached.
Lock_Flag
Lock flag detected.
Network_Change_Event
Network change event (NCE) occurred.
Shutdown_Flag
Shutdown flag detected.
Network_Activity_End
Network activity ends.
Network_Activity
Network activity detected.
6.3.1.3 NetInterface_Transition
NetInterface_Transition corresponds to events that are used to notify the application about
transitions from one NetInterface state to another.
REQ 4.3 Service interface – Parameters – NL/TL to upper layers – NetInterface_Transition
The NetInterface_Transition values shall be of data type Enum and shall contain the value specified
according to Table 3.
Table 3 — NetInterface_Transition values
Enum value Description
ev_Wake_Up
The ev_Wake_Up transition from
s_NetInterface_Sleep to s_NetInterface_Off is taken.
ev_Sleep
The ev_Sleep transition from
s_NetInterface_Off to s_NetInterface_Sleep is taken.
ev_Start_Up
The ev_Start_Up transition from
s_NetInterface_Off to s_NetInterface_Init is taken.
ev_Diagnosis_Start
The ev_Diagnosis_Start transition from s_NetInterface_Off to
s_NetInterface_Diagnosis is taken.
ev_Init_Error_Shutdown
The ev_Init_Error_Shutdown transition from s_NetInterface_Init to
s_NetInterface_Off is taken.
ev_Init_Diagnosis_Start
The ev_Init_Diagnosis_Start transition from s_NetInterface_Init to
s_NetInterface_Diagnosis is taken.
ev_Init_Ready
The ev_Init_Ready transition from s_NetInterface_Init to
s_NetInterface_Normal_Operation is taken.
ev_Error_Shutdown
The ev_Error_Shutdown transition from s_NetInterface_Normal_
Operation to
s_NetInterface_Off is taken.
ev_Normal_Shutdown
The ev_Normal_Shutdown transition from s_NetInterface_Normal_
Operation to
s_NetInterface_Off is taken.
ev_Diagnosis_Ready
The ev_Diagnosis_Ready transition from s_NetInterface_Diagnosis to
s_NetInterface_Normal_Operation is taken.
Table 3 (continued)
Enum value Description
ev_Diagnosis_End
The ev_Diagnosis_End transition from s_NetInterface_Diagnosis to
s_NetInterface_Off is taken.
6.3.1.4 DiagResult
DiagResult corresponds to the possible diagnosis to be provided to the application. The structure
of DiagResult depends on the kind of diagnosis that is performed and should be adopted from the
corresponding specification.
REQ 4.4 Service interface – Parameters – NL/TL to upper layers – DiagResult
The DiagResult values for ring break diagnosis, as specified in Annex A (informative), shall be of data type
Enum and shall contain the value specified according to Table 4.
Table 4 — DiagResult values for ring break diagnosis
Enum value Description
No_Error
No error detected.
Ring_Break
Ring break detected. The result indicates the relative position of ring break
in the Relative_Position parameter.
Weak_Signal
Excessive attenuation detected at the input.
Diagnosis_Inconclusive
The ring break diagnosis inconclusive.
6.3.1.5 Relative_Position
The content of the Relative_Position parameter is relevant if the DiagResult parameter contains the
value Ring_Break.
REQ 4.5 Service interface – Parameters – NL/TL to upper layers – Relative_Position
The Relative_Position parameter shall be of data type Unsigned Byte and shall contain the relative posi-
tion of the node to a ring break.
6.3.1.6 Shutdown_Reason
Shutdown_Reason corresponds to the possible causes of a shutdown to be provided to the application.
REQ 4.6 Service interface – Parameters – NL/TL to upper layers – Shutdown_Reason
The Shutdown_Reason parameter shall be of data type Enum and shall contain the value specified according to
Table 5.
Table 5 — Shutdown_Reason values
Enum value Description
No_Result_Available
Initial value of the shutdown reason.
No_Fault_Saved
Shutdown flag detected before network activity ceased.
Sudden_Signal_Off
Shutdown caused by a sudden signal off (SSO).
Critical_Unlock
Shutdown caused by a critical unlock.
6 © ISO 2020 – All rights reserved

6.3.1.7 Node_Position
Node_Position provides the current node position to the application.
REQ 4.7 Service interface – Parameters – NL/TL to upper layers – Node_Position
The Node_Position parameter shall be of data type Unsigned Byte and shall contain the current node position.
6.3.1.8 Maximum_Position
Maximum_Position provides the maximum node position information to the application.
REQ 4.8 Service interface – Parameters – NL/TL to upper layers – Maximum_Position
The Maximum_Position parameter shall be of data type Unsigned Byte and shall contain the maximum node
position information.
6.3.1.9 Transmission_Status
Transmission_Status corresponds to the possible outcomes of a message transmission to be provided
to the application.
REQ 4.9 Service interface – Parameters – NL/TL to upper layers – Transmission_Status
The Transmission_Status parameter shall be of data type Enum and shall contain the value specified
according to Table 6.
Table 6 — Transmission_Status values
Enum value Description
Success
The message is transmitted successfully.
Buffer_Full
The receiver buffer is full.
CRC_Error
A CRC error occurred.
Wrong_Target
There is no such target.
Segmentation_Error_01
First segment missing, that is, the first telegram of a segmented transfer is
not received.
Segmentation_Error_02
Target node does not provide enough buffers to handle a message of this size.
Segmentation_Error_03
Unexpected segment number
Segmentation_Error_04
Too many unfinished segmentation messages pending.
Segmentation_Error_05
Timeout while waiting for next segment.
Segmentation_Error_06
Node not capable of handling segmented transfers.
Segmentation_Error_07
Segmented transfer has not been finished before the arrival of another mes-
sage with identical MsgID sent by the same node.
6.3.2 Parameters — Upper layers to TL/NL
6.3.2.1 Overview
Table 7 specifies the parameters that are used in the service interface and received from upper layers.
Table 7 — Parameters received from upper layers to TL/NL
Parameter Data type Description
Application_Request
Enum { A request from the application; it is
cmd_Network_Startup, passed from upper layers to NL/TL.
cmd_Off_Request,
cmd_Emergency_Shutdown,
cmd_Start_Diagnosis,
cmd_DiagResult,
cmd_Shutdown_Reason
}
Network_Startup_Type
Enum { Determines how a node starts up.
TimingMaster,
TimingSlave
}
Number_Of_Retries Unsigned Byte
The number of low-level retries to
perform on a control data trans-
mission.
Priority Unsigned Byte
The priority for a control data
transmission
Group_Address Unsigned Word
A group address
Node_Address Unsigned Word
A logical node address
EUI_48 EUI-48
A 48-bit address
Bandwidth Unsigned Word
Required bandwidth
6.3.2.2 Application_Request
Application_Request corresponds to actions that the application can request from lower layers. These
requests require no additional information.
REQ 4.10 Service interface – Parameters – Upper layers to TL/NL – Application_Request
The Application_Request values shall be of data type Enum and shall contain the value specified according to
Table 8.
Table 8 — Application_Request values
Enum value Description
cmd_Network_Startup
Network startup requested.
cmd_Off_Request
Off Request issued.
cmd_Emergency_Shutdown
Emergency shutdown requested.
cmd_Start_Diagnosis
Start of diagnosis requested. The network owner determines how the kind
of diagnosis to be performed is selected, for example, through an additional
action or by hard coding it.
cmd_DiagResult
DiagResult of the diagnosis requested.
cmd_Shutdown_Reason
Shutdown reason requested.
6.3.2.3 Network_Startup_Type
The Network_Startup_Type corresponds to the two different startup types, which can be chosen for the
MOST network controller.
REQ 4.11 Service interface – Parameters – Upper layers to TL/NL – Network_Startup_Type
The Network_Startup_Type parameter shall be of data type Enum and shall contain the value specified
according to Table 9.
8 © ISO 2020 – All rights reserved

Table 9 — Network_Startup_Type values
Enum value Description
TimingMaster
For startup, configure the MOST network controller as TimingMaster.
TimingSlave
For startup, configure the MOST network controller as TimingSlave.
6.3.2.4 Number_Of_Retries
Number_Of_Retries is used to set the maximum permissible number of low-level retries for a particular
message.
REQ 4.12 Service interface – Parameters – Upper layers to TL/NL – Number_Of_Retries
The Number_Of_Retries parameter shall be of data type Unsigned Byte and shall contain the maximum
permissible number of low-level retries for a particular message.
6.3.2.5 Priority
Priority is used by the application to set the priority for a particular message.
REQ 4.13 Service interface – Parameters – Upper layers to TL/NL – Priority
The Priority parameter shall be of data type Unsigned Byte and shall contain priority for a particular message.
6.3.2.6 Group_Address
Group_Address is an Unsigned Word parameter, which is used to set the group address of the node.
REQ 4.14 Service interface – Parameters – Upper layers to TL/NL – Group_Address
The Group_Address parameter shall be of data type Unsigned Word and shall contain the group address of
the node.
6.3.2.7 Node_Address
Node_Address is an Unsigned Word parameter, which is used to set the logical node address of the node.
REQ 4.15 Service interface – Parameters – Upper layers to TL/NL – Node_Address
The Node_Address parameter shall be of data type Unsigned Word and shall contain the logical node address
of the node.
6.3.2.8 EUI_48
EUI_48 is used to set the MAC address of the node.
REQ 4.16 Service interface – Parameters – Upper layers to TL/NL – EUI_48
The EUI_48 parameter shall be of data type EUI-48 and shall contain the MAC address of the node.
6.3.2.9 Bandwidth
Bandwidth is used to request the allocation of the corresponding number of bytes in the network frame.
REQ 4.17 Service interface – Parameters – Upper layers to TL/NL – Bandwidth
The Bandwidth parameter shall be of data type Unsigned Word and shall contain the number of bytes in the
network frame that are requested for allocation.
6.3.3 Parameters – NL/TL to upper layers and upper layers to TL/NL
6.3.3.1 Overview
Table 10 provides an overview of the parameters that are used in the specified service interface and
used in both directions.
Table 10 — Parameters passed from NL/TL to upper layers and upper layers to TL/NL
Parameter Data type Description
Media_Interface_ID Unsigned Word
An identifier for media data output or input
Length Unsigned Word
Length of the data field that is contained in the same
service interface.
Data Byte Array
A data field, whose length is determined by the Length
parameter.
MsgID Unsigned Long
The MsgID field for control data
Session_ID Unsigned Word
A session identifier to correlate confirmations to
send-operations.
Target_Address Unsigned Word
A 16-bit target address
Source_Address Unsigned Word
A 16-bit source address
Destination_MAC_Address EUI-48
A 48-bit target address
Source_MAC_Address EUI-48
A 48-bit source address
6.3.3.2 Media_Interface_ID
Media_Interface_ID is used to unambiguously identify a media interface as source or target of
streaming data.
REQ 4.18 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL –
Media_Interface_ID
The Media_Interface_ID parameter shall be of data type Unsigned Word and shall identify a media interface.
6.3.3.3 Length
Length is used to provide the size of the data field that is contained in the same service interface.
REQ 4.19 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL – Length
The Length parameter shall be of data type Unsigned Byte and shall contain the size of the data field that is
contained in the same service interface.
6.3.3.4 Data
Data is used as a wrapper for payload that requires no interpretation in the context of the service
interface that contains it.
REQ 4.20 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL – Data
The Data parameter shall be of data type Byte Array.
6.3.3.5 MsgID
MsgID is used to identify the target of a control frame.
REQ 4.21 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL – MsgID
The MsgID parameter shall be of data type Unsigned Long and shall identify the target of a control frame.
10 © ISO 2020 – All rights reserved

6.3.3.6 Session_ID
Session_ID is an Unsigned Word parameter, which is used to unambiguously identify an instance of a
control frame that is passed down by the application. The session ID is generated by the application and
used when determining the outcome of a transmission attempt.
REQ 4.22 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL –
Session_ID
The Session_ID parameter shall be of data type Unsigned Word and shall identify an instance of a control frame.
6.3.3.7 Target_Address
Target_Address is used to fill the target address field for 16-bit addressing for control data and
packet data.
REQ 4.23 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL –
Target_Address
The Target_Address parameter shall be of data type Unsigned Word and shall contain the target address for
16-bit addressing for control data and packet data.
6.3.3.8 Source_Address
Source_Address is used to fill the source address field for 16-bit addressing for control data and
packet data.
REQ 4.24 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL –
Source_Address
The Source_Address parameter shall be of data type Unsigned Word and shall contain the source address for
16-bit addressing for control data and packet data.
6.3.3.9 Destination_MAC_Address
Destination_MAC_Address is used to fill the destination address field for 48-bit addressing.
REQ 4.25 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL –
Destination_MAC_Address
The Destination_MAC_Address parameter shall be of data type EUI-48 and shall contain the destination
address for 48-bit addressing.
6.3.3.10 Source_MAC_Address
Source_MAC_Address is used to fill the source address field for 48-bit addressing.
REQ 4.26 Service interface – Parameters – NL/TL to upper layers and upper layers to TL/NL –
Source_MAC_Address
The Source_MAC_Address parameter shall be of data type EUI-48 and shall contain the source address for 48-
bit addressing.
6.4 Event indications and action requests
6.4.1 N_EVENT.INDICATE
REQ 4.27 Service interface – Event indications and action requests – N_EVENT.INDICATE
The N_EVENT.INDICATE shall be passed from NL/TL to upper layers to indicate that an event has occurred.
N_EVENT.INDICATE shall comply with the following structure:
N_EVENT.INDICATE{
Application_Event
}
6.4.2 N_NODE_POSITION.INDICATE
REQ 4.28 Service interface – Event indications and action requests – N_NODE_POSITION.INDICATE
The N_NODE_POSITION.INDICATE primitive shall be passed from NL/TL to upper layers to indicate the node
position.
N_NODE_POSITION.INDICATE shall comply with the following structure:
N_NODE_POSITION.INDICATE{
Node_Position
}
6.4.3 N_MAXIMUM_NODE_POSITION.INDICATE
REQ 4.29 Service interface – Event indications and action requests –
N_MAXIMUM_NODE_POSITION.INDICATE
The N_MAXIMUM_NODE_POSITION.INDICATE primitive shall be passed from NL/TL to upper layers to indicate
the maximum node position.
N_MAXIMUM_NODE_POSITION.INDICATE shall comply with the following structure:
N_MAXIMUM_NODE_POSITION.INDICATE{
Maximum_Position
}
6.4.4 N_NET_INTERFACE_TRANSITION.INDICATE
REQ 4.30 Service interface – Event indications and action requests –
N_NET_INTERFACE_TRANSITION.INDICATE
The N_NET_INTERFACE_TRANSITION.INDICATE primitive shall be passed from NL/TL to upper layers to indi-
cate that an event has occurred.
N _NET_INTERFACE_TRANSITION.INDICATE shall comply with the following structure:
N_EVENT.INDICATE{
NetInterface_Transition
}
12 © ISO 2020 – All rights reserved

6.4.5 N_DIAGRESULT.INDICATE
The content of the Relative_Position parameter is relevant if the DiagResult parameter contains the
value Ring_Break.
REQ 4.31 Service interface – Event indications and action requests – N_DIAGRESULT.INDICATE
The N_DIAGRESULT.INDICATE primitive shall be passed from NL/TL to upper layers to provide the
DiagResult.
N_DIAGRESULT.INDICATE shall comply with the following structure:
N_DIAGRESULT.INDICATE{
DiagResult
Relative_Position
}
6.4.6 N_SHUTDOWN_REASON.INDICATE
N_SHUTDOWN_REASON.INDICATE is returned as response to N_ACTION.REQUEST when the Application_
Request parameter contains the value Shutdown_Reason.
REQ 4.32 Service interface – Event indications and action requests –
N_SHUTDOWN_REASON.INDICATE
The N_SHUTDOWN_REASON.INDICATE primitive shall be passed from NL/TL to upper layers to provide the shut-
down reason.
N_SHUTDOWN_REASON.INDICATE shall comply with the following structure:
N_SHUTDOWN_REASON.INDICATE{
Shutdown_Reason
}
6.4.7 N_ACTION.REQUEST
REQ 4.33 Service interface – Event indications and action requests – N_ACTION.REQUEST
The N_ACTION.REQUEST primitive shall be passed from upper layers to NL/TL to trigger execution of a request.
N_ACTION.REQUEST shall comply with the following structure:
N_ACTION.REQUEST{
Application_Request
}
6.4.8 N_NETWORK_STARTUP.REQUEST
REQ 4.34 Service interface – Event indications and action requests –
N_NETWORK_STARTUP.REQUEST
The N_NETWORK_STARTUP.REQUEST primitive shall be passed from upper layers to NL/TL to trigger network
startup.
N_NETWORK_STARTUP.REQUEST shall comply with the following structure:
N_NETWORK_STARTUP.REQUEST{
Network_Startup_Type
}
6.4.9 N_SET_GROUP_ADDRESS.REQUEST
REQ 4.35 Service interface – Event indications and action requests –
N_SET_GROUP_ADDRESS.REQUEST
The N_SET_GROUP_ADDRESS.REQUEST primitive shall be passed from upper layers to NL/TL to set the group
address of the node.
N_SET_GROUP_ADDRESS.REQUEST shall comply with the following structure:
N_SET_GROUP_ADDRESS.REQUEST{
Group_Address
}
6.4.10 N_SET_NODE_ADDRESS.REQUEST
REQ 4.36 Service interface – Event indications and action requests –
N_SET_NODE_ADDRESS.REQUEST
The N_SET_NODE_ADDRESS.REQUEST primitive shall be passed from upper layers to NL/TL t
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