Intelligent transport systems -- Localized communications -- Communication protocol messages for global usage

This document specifies: —   the Localized Message (LM) format: an NPDU of a networking & transport layer protocol that does not support routing of a packet through a network; —   the Service Advertisement Message (SAM): an APDU to be transported in an LM, for example; —   the Service Response Message (SRM): an APDU acknowledging a SAM that offered a service based on an ITS application class[2] to be transported in an LM, for example; —   related basic requirements for procedures. Specifications are partly done by normative references to IEEE 1609.3(TM)-2016. NOTE      These message format specifications and basic procedures need to be complemented by complete procedures and SAP specifications according to the context of usage, i.e. an ITS station specified in ISO 21217, or a WAVE device specified in IEEE 1609.0[13] or any other context.

Systèmes de transport intelligents -- Communications localisées -- Messages de protocole de communication pour une utilisation globale

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Published
Publication Date
19-Apr-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
19-Mar-2021
Completion Date
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INTERNATIONAL ISO
STANDARD 16460
First edition
2021-04
Intelligent transport systems —
Localized communications —
Communication protocol messages for
global usage
Systèmes de transport intelligents — Communications localisées —
Messages de protocole de communication pour une utilisation globale
Reference number
ISO 16460:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 16460:2021(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 16460:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 1

5 Localized communications messages ............................................................................................................................................. 3

5.1 Purpose .......................................................................................................................................................................................................... 3

5.2 Localized message protocol ......................................................................................................................................................... 3

5.3 Message formats .................................................................................................................................................................................... 3

5.4 Networking features........................................................................................................................................................................... 4

5.4.1 Subtype values ................................................................................................................................................................... 4

5.4.2 Networking feature 0 ................................................................................................................................................... 5

5.4.3 Networking feature 1 ................................................................................................................................................... 5

5.4.4 Networking feature 2 ................................................................................................................................................... 6

5.4.5 N-Extensions ....................................................................................................................................................................... 7

5.4.6 TPID values ........................................................................................................................................................................... 7

5.5 Transport features ............................................................................................................................................................................... 8

5.5.1 Transport feature 0 ........................................................................................................................................................ 8

5.5.2 Transport feature 1 ........................................................................................................................................................ 9

5.5.3 Transport feature 2 .....................................................................................................................................................10

5.5.4 T-Extensions......................................................................................................................................................................11

5.5.5 ITS port numbers .........................................................................................................................................................11

5.6 Procedures ...............................................................................................................................................................................................11

6 Service advertisement messages ......................................................................................................................................................12

6.1 Purpose .......................................................................................................................................................................................................12

6.2 Unique identifiers ..............................................................................................................................................................................12

6.2.1 ITS-AID/PSID ...................................................................................................................................................................12

6.2.2 ITS port numbers (ITS-PNs) ...............................................................................................................................13

6.3 Service advertisement protocol ............................................................................................................................................13

6.4 Service advertisement message (SAM) ...........................................................................................................................13

6.4.1 Messages ..............................................................................................................................................................................13

6.4.2 Message structure ........................................................................................................................................................13

6.4.3 Message header .............................................................................................................................................................14

6.4.4 Message body ...................................................................................................................................................................16

6.5 Service Response Message (SRM) .......................................................................................................................................22

6.5.1 Message structure ........................................................................................................................................................22

6.5.2 Message header .............................................................................................................................................................23

6.5.3 Message body ...................................................................................................................................................................23

6.6 Count N .......................................................................................................................................................................................................27

6.7 Procedures ...............................................................................................................................................................................................27

6.7.1 General...................................................................................................................................................................................27

6.7.2 Privately allocated channels ...............................................................................................................................27

6.8 Secured messages ..............................................................................................................................................................................28

7 Structure of extension elements .......................................................................................................................................................29

Annex A (normative) ASN.1 modules ................................................................................................................................................................31

Bibliography .............................................................................................................................................................................................................................45

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 16460:2021(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/d irectives).

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/p atents).

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/f oreword. html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

This first edition cancels and replaces the first edition (ISO/TS 16460:2016), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— editorial improvements;
— editorial corrections.

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/m embers. html.
iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 16460:2021(E)
Introduction

This document belongs to a set of International Standards for Intelligent Transport Systems (ITS) and

Cooperative ITS (C-ITS). An introduction to this set of International Standards is provided in ISO 21217.

Localized communications, i.e. communications without networking through nodes, and service

advertisement are essential protocol functionalities in C-ITS. ISO and IEEE developed protocols with

similar functionality, i.e. the
— ISO Fast Networking & Transport Protocol (FNTP) standardized in ISO 29281-1;
[15]
— IEEE WAVE Short Message Protocol (WSMP) standardized in IEEE 1609.3 ,
— ISO Fast Service Advertisement Protocol (FSAP) standardized in ISO 24102-5,
[15]
— IEEE WAVE Service Advertisement (WSA) standardized in IEEE 1609.3 ,

where ISO considered the architectural context of an ITS station specified in ISO 21217:2014, and IEEE

[13]
considered the architectural context of a WAVE device specified in IEEE 1609.0 .

Although initial versions of these protocols from ISO and IEEE are very similar, there are differences

in details of the message formats and the functionality. These differences were identified by the EU/US

[20]

task force HTG 3, from which a recommendation resulted to harmonize the protocols .

The result of harmonization of FNTP with WSMP, and of FSAP with WSA is presented in this document,

distinguishing interoperability modes, and enhanced features specified in this document.

With reference to this document, the initial editions of ISO 29281-1 and IEEE 1609.3 were revised, and

ISO 24102-5 was converted into EN ISO 22418, enabling global interoperability of equipment designed

for different architectures. Finally, ETSI developed EN 302 890-1 (a further service announcement

protocol profile) with reference to the previous edition of this document, i.e. ISO/TS 16460:2016.

© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 16460:2021(E)
Intelligent transport systems — Localized communications
— Communication protocol messages for global usage
1 Scope
This document specifies:

— the Localized Message (LM) format: an NPDU of a networking & transport layer protocol that does

not support routing of a packet through a network;

— the Service Advertisement Message (SAM): an APDU to be transported in an LM, for example;

— the Service Response Message (SRM): an APDU acknowledging a SAM that offered a service based

[2]
on an ITS application class to be transported in an LM, for example;
— related basic requirements for procedures.
Specifications are partly made by normative references to IEEE 1609.3(TM)-2016.

NOTE These message format specifications and basic procedures need to be complemented by complete

procedures and SAP specifications according to the context of usage, i.e. an ITS station specified in ISO 21217, or

[13]
a WAVE device specified in IEEE 1609.0 or any other context.
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/IEC 8824-1, Information technology — Abstract Syntax Notation One (ASN.1): Specification of basic

notation

IEEE 1609.3(TM)-2016: Standard for Wireless Access in Vehicular Environments (WAVE) — Networking

Services
3 Terms and definitions
No terms and definitions are listed in this document.

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/
4 Symbols and abbreviated terms
CIP communication interface parameter
C-ITS cooperative ITS
DNS domain name server
EIRP effective isotropic radiated power
© ISO 2021 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 16460:2021(E)
ESAP ETSI Service Announcement Protocol
FNTP Fast Networking & Transport Protocol
FSAP Fast Service Advertisement Protocol
HTG Harmonization Task Group
IPv6 Internet Protocol version 6
ITS Intelligent Transport Systems
ITS-AID ITS application identifier
ITS-PN ITS port number
LM localized message
LPP Local Port Protocol
MAC medium access control
NPDU network protocol data unit
OER octet encoding rules
OSI open system interconnection
PSID provider service identifier
RX CIP receiver CIP
SAM service advertisement message
SAM-ID SAM identifier
SAM-Count SAM change of content identifier
SAP service access point
SRM service response message
TCP transmission control protocol
TPID transport protocol identifier
TX CIP transmitter CIP
UPER unaligned packet encoding rules
VANET vehicular ad-hoc network
WAVE wireless access in vehicular environment
WSA WAVE service advertisement
WSMP WAVE short message protocol
2 © ISO 2021 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 16460:2021(E)
5 Localized communications messages
5.1 Purpose

Localized communication is used to communicate with nearby peer stations, e.g. ITS station units or

WAVE devices. These stations are uniquely identified with an OSI data link layer address, typically

by the MAC address. Networking in the sense of IP networking, where stations route packets to other

nodes through a network (cloud), is not supported. Nevertheless, multi-hopping can be performed in

different ways, e.g.:

— N-hop broadcast or N-hop multicast, which requires careful means to avoid flooding of the

communication channel;
[4]

— dedicated forwarding performed at higher layers, e.g. at the ITS-S facilities layer of an ITS station ;

this is a feature useful for geo-dissemination of information,

which create so-called "Vehicular Ad-hoc NETworks" (VANETs). Routing of packets through a network

in ITS will use the Internet protocol version 6 (IPv6).
5.2 Localized message protocol

As this document does not specify a specific localized communications protocol but just the structure

of messages of such protocols and related basic requirements, a hypothetical localized communications

protocol with the name "Localized Message Protocol" is used to simplify reading of the document.

5.3 Message formats

Figure 1 illustrates the basic format of the LM. Unaligned packet encoding rules UPER applied to the

ASN.1 type LMnpdu defined in A.2.1 result in the intended binary presentation of this LM format.

NOTE In Figure 1 the "TPID" field (specified in IEEE 1609.3(TM)-2016 as a 1-octet unsigned Integer field

completely allocated in the WSMP-N-Header) is split into a "Feature selector" field of the "N-Header" and a

"T-Extensions flag" field of the "T-Header" (according to the general rules of the OSI model). However, the two

presentations result in identical binary presentations.
Figure 1 — General format of the LM NPDU
The LM consists of three parts:
— "N-Header"

— A 4-bit unsigned Integer "Subtype" number in the range of 0 to 15 indicating a networking

related feature.
— A 1-bit "N-Extensions flag".

— A 3-bit unsigned Integer "Version" number in the range of 0 to 7 indicating the version of

the localized message protocol. In case a receiver does not support the version, the received

packet cannot be processed. The first version number used is three in accordance with

IEEE 1609.3(TM):2016.
© ISO 2021 – All rights reserved 3
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ISO 16460:2021(E)

NOTE 1 The format presented in Figure 1 is such that WAVE devices implementing version 2 of

[15]
WSMP can identify LMs as WSMP messages with version number 3 or higher.

— A networking related feature specified in 5.4 and selected by the value contained in the field

"Subtype".
— "N-Extensions" being present if the "N-Extensions flag" is set to '1'b.

— A 7-bit unsigned Integer in the range of 0 to 127, the " TPID - Feature selector", indicating content

in the "T-Header".
— "T-Header".
— A 1-bit "TPID - T-Extensions flag".

— A transport related feature specified in 5.5 and selected by the TPID - Feature selector value

contained in the "N-Header".
— "T-Extensions" being present if the "T-Extension flag" is set to '1'b.

— A one or two octet field indicating the number of octets contained in "User data".

— Body.
— The "User data".

The distinction of "N-Header" (networking related features) and "T-Header" (transport related features)

is in line with the OSI layers 3 and 4; these two OSI layers constitute the ITS-S networking & transport

layer as illustrated in ISO 21217.

The field "Length of User data" has a length of one or two octets dependent on the value contained in it:

— One octet size: Values from 0 through 127. The most significant bit is always set to zero. Presentation

as 0x00 (=0) through 0xEF (=127), i.e. the remaining 7 bits contain an unsigned integer number.

— Two octet size: Values from 128 through 16383. The most significant bit of the first octet is

always set to one, and the second most significant bit of the first octet is always set to zero.

Presentation as 0x8080 (=128) through 0xBFFF (=16383), i.e. the remaining 14 bits contain an

unsigned integer number.

NOTE 2 This presentation results from the unaligned packed encoding rules applied to ASN.1 types of

unconstraint variable length.
5.4 Networking features
5.4.1 Subtype values

Networking features are identified by a Subtype value. Subtype values are presented in Table 1.

Table 1 — Subtype values
Subtype N-Extensions N-Extensions Networking related fea- Remark
flag tures
0 '0'b Not present Null-Networking Mandatory feature specified in
IEEE 1609.3(TM)-2016. Format
'1'b Present
specified in 5.4.2.
1 '0'b Not present ITS station-internal forwarding Format specified in 5.4.3.
'1'b Present
2 '0'b Not present N-hop forwarding Format specified in 5.4.4.
'1'b Present
4 © ISO 2021 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 16460:2021(E)
Table 1 (continued)
Subtype N-Extensions N-Extensions Networking related fea- Remark
flag tures
3 '0'b Not present Geo-forwarding Reserved. Not specified in this
version of the Document.
'1'b Present
4 - 7 '0'b Not present Reserved for ISO Allows for further four networking
features.
'1'b Present
8 - 15 '0'b Not present Reserved for IEEE Allows for further eight networking
features.
'1'b Present
N-Extensions and related basic procedures shall be as specified in 5.4.5.

New networking features can be specified and linked to so far reserved Subtype values at a later stage

without breaking backward compatibility.
5.4.2 Networking feature 0
Subtype 0 selects the "Null-Networking" feature introduced in 5.4.1.

NOTE Procedures on how to use this feature in the context of an ITS station unit, or a WAVE device, or any

other context are outside the scope of this document.

The "Null-Networking" feature with Subtype 0 is the uppermost simple feature, as it requires only

processing of the TPID - Feature selector field specified in 5.6. Figure 2 presents the N-Header format

for Subtype 0 with N-Extensions being absent.
Figure 2 — N-Header for Subtype 0 without N-Extensions

Figure 3 presents the N-Header format for Subtype 0 with N-Extensions being present.

Figure 3 — N-Header for Subtype 0 with N-Extensions
N-Extensions and related basic procedures shall be as specified in 5.4.5.
5.4.3 Networking feature 1

Subtype 1 selects the "ITS Station-Internal Forwarding" feature introduced in 5.4.1.

NOTE Procedures on how to use this feature in the context of an ITS station unit, or a WAVE device, or any

other context are outside the scope of this document.

ITS station-internal forwarding is a feature applicable in ITS stations conformant with ISO 21218 (Link-

ID) and ISO 24102-4 (ITS-SCU-ID). It is used to forward packets between router units and host units that

are part of the same station/device. The field "Direction" contains an unsigned integer number with the

© ISO 2021 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 16460:2021(E)

two possible values "0" ("from host to router") and "255" ("from router to host"). The field "Counter"

contains a 1-octet unsigned integer cyclic packet counter being unique in the unit that forwards a

packet. Figure 4 presents the N-Header format for Subtype 1 with N-Extensions being absent.

Figure 4 — N-Header for Subtype 1 without N-Extensions

Figure 5 presents the N-Header format for Subtype 1 with N-Extensions being present.

Figure 5 — N-Header for Subtype 1 with N-Extensions

NOTE In Figure 5, unlike in the presentation in Figure 1, subtype-specific elements (i.e. "Original

N-Header") are allocated between "N-Extensions" and "TPID - Feature Selector". This is to simplify processing

at the receiver side.
N-Extensions and related basic procedures shall be as specified in 5.4.5.
5.4.4 Networking feature 2
Subtype 2 select the "N-hop Forwarding" feature introduced in 5.4.1.

NOTE Procedures on how to use this feature in the context of an ITS station unit, or a WAVE device, or any

other context are outside the scope of this document.

N-hop forwarding is a feature that allows extending the communication range for information

dissemination (MAC broadcast or multicast mode) beyond the next directly reachable neighbour

stations. It uses parameters that allow flooding of the communication channel to be avoided. Figure 6

presents the N-Header format for Subtype 2 with N-Extensions being absent.
Figure 6 — N-Header for Subtype 2 without N-Extensions

The 22-bit Message ID is generated from a random number generator and is unique within the N-hop

communication range with a "high" likelihood. In case of duplicate Message ID values, forwarding might

not be performed correctly in a station.

The 2-bit unsigned Integer Hop Count indicates to a receiver whether a forwarding shall be performed

or not. If the Hop Count equals zero, forwarding is prohibited. Prior to forwarding of a packet, the Hop

Count shall be decremented by one. Consequently, a maximum of four hops is possible.

6 © ISO 2021 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 16460:2021(E)

Forwarding shall be performed also if the TPID value contained in the received message is not supported

or is reserved.

Figure 7 presents the N-Header format for Subtype 2 with N-Extensions being present.

Figure 7 — N-Header for Subtype 2 with N-Extensions
N-Extensions and related procedures shall be as specified in 5.4.5.
5.4.5 N-Extensions

The structure of the N-Extensions is specified in Clause 7. Extension elements presented in Table 2 may

be used in the "N-Extensions" field.
Table 2 — N-Extensions elements
Element ID Element type (ASN.1) Element name
TXpower80211
c-TxPowerUsed80211= 4 Transmit Power Used (specified in
IEEE 1609.3(TM)-2016).
ChannelNumber80211
c-ChannelNumber80211 = 15 802.11 Channel Number used (specified in
IEEE 1609.3(TM)-2016).
DataRate80211
c-DataRate80211 = 16 802.11 Data Rate used (specified in
IEEE 1609.3(TM)-2016).
TXcip
c-LMtxCip = 80 Communication Interface transmit pa-
rameters.
RXcip
c-LMrxCip = 81 Communication Interface receive param-
eters (RX-CIP).
LMchannelBusyRatio
c-LMchannelBusyRatio = 82 Channel Busy Ratio.

The "Transmit Power Used" element is optionally included in the LM N-Header for use by the LM

[12]
recipient; see also IEEE Std 802.11 .

The "Channel Number" element is optionally included in the LM N-Header for use by the LM recipient;

[12]
see also IEEE Std 802.11 .

The "Data Rate" element is optionally included in the LM N-Header for use by the LM recipient; see also

[12]
IEEE Std 802.11 .

The "TX CIP" element is optionally included in the LM N-Header indicating CIP settings used by the

transmitter of the LM.

The "RX CIP" element is optionally included in the LM N-Header used with Subtype 1 indicating CIP

settings of the ITS-SCU that received the LM from a peer station.

The "Channel Busy Ratio" element is a one octet unsigned integer optionally included in the LM

N-Header reporting the observed channel busy ratio in percent (0 % up to 100 % in steps of 0,5 %). The

integer values 201 through 255 indicate "unknown ratio".
5.4.6 TPID values
Table 3 provides a summary of TPID values.
© ISO 2021 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO 16460:2021(E)
Table 3 — TPID values
TPID T-Extensions Transport related feature Remark
Feature T-Extensions
selector flag
0 '0'b Not present Information dissemination Mandatory feature specified in
IEEE 1609.3(TM)-2016. Format spec-
'1'b Present
ified in 5.5.1.
1 '0'b Not present General session mode Format specified in 5.5.2,
'1'b Present
2 '0'b Not present LPP mode Format specified in 5.5.3.
'1'b Present

3 - 10 '0'b Not present Reserved for ISO Allows for further 8 transport features.

'1'b Present
11 - 127 '0'b Not present Reserved for IEEE Allows for further 117 transport
features.
'1'b Pres
...

INTERNATIONAL ISO
STANDARD 16460
First edition
Intelligent transport systems —
Localized communications —
Communication protocol messages for
global usage
Systèmes de transport intelligents — Communications localisées —
Messages de protocole de communication pour une utilisation globale
PROOF/ÉPREUVE
Reference number
ISO 16460:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 16460:2021(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 16460:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 1

5 Localized communications messages ............................................................................................................................................. 3

5.1 Purpose .......................................................................................................................................................................................................... 3

5.2 Localized message protocol ......................................................................................................................................................... 3

5.3 Message formats .................................................................................................................................................................................... 3

5.4 Networking features........................................................................................................................................................................... 4

5.4.1 Subtype values ................................................................................................................................................................... 4

5.4.2 Networking feature 0 ................................................................................................................................................... 5

5.4.3 Networking feature 1 ................................................................................................................................................... 5

5.4.4 Networking feature 2 ................................................................................................................................................... 6

5.4.5 N-Extensions ....................................................................................................................................................................... 7

5.4.6 TPID values ........................................................................................................................................................................... 7

5.5 Transport features ............................................................................................................................................................................... 8

5.5.1 Transport feature 0 ........................................................................................................................................................ 8

5.5.2 Transport feature 1 ........................................................................................................................................................ 9

5.5.3 Transport feature 2 .....................................................................................................................................................10

5.5.4 T-Extensions......................................................................................................................................................................11

5.5.5 ITS port numbers .........................................................................................................................................................11

5.6 Procedures ...............................................................................................................................................................................................11

6 Service advertisement messages ......................................................................................................................................................12

6.1 Purpose .......................................................................................................................................................................................................12

6.2 Unique identifiers ..............................................................................................................................................................................12

6.2.1 ITS-AID/PSID ...................................................................................................................................................................12

6.2.2 ITS port numbers (ITS-PNs) ...............................................................................................................................13

6.3 Service advertisement protocol ............................................................................................................................................13

6.4 Service advertisement message (SAM) ...........................................................................................................................13

6.4.1 Messages ..............................................................................................................................................................................13

6.4.2 Message structure ........................................................................................................................................................13

6.4.3 Message header .............................................................................................................................................................14

6.4.4 Message body ...................................................................................................................................................................16

6.5 Service Response Message (SRM) .......................................................................................................................................22

6.5.1 Message structure ........................................................................................................................................................22

6.5.2 Message header .............................................................................................................................................................23

6.5.3 Message body ...................................................................................................................................................................23

6.6 Count N .......................................................................................................................................................................................................27

6.7 Procedures ...............................................................................................................................................................................................27

6.7.1 General...................................................................................................................................................................................27

6.7.2 Privately allocated channels ...............................................................................................................................27

6.8 Secured messages ..............................................................................................................................................................................28

7 Structure of extension elements .......................................................................................................................................................29

Annex A (normative) ASN.1 modules ................................................................................................................................................................31

Bibliography .............................................................................................................................................................................................................................45

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 16460:2021(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/d irectives).

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/p atents).

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/f oreword. html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

This first edition cancels and replaces the first edition (ISO/TS 16460:2016), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— editorial improvements.
— editorial corrections.

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/m embers. html.
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ISO 16460:2021(E)
Introduction

This document belongs to a set of International Standards for Intelligent Transport Systems (ITS) and

Cooperative ITS (C-ITS). An introduction to this set of International Standards is provided in ISO 21217.

Localized communications, i.e. communications without networking through nodes, and service

advertisement are essential protocol functionalities in C-ITS. ISO and IEEE developed protocols with

similar functionality, i.e. the
— ISO Fast Networking & Transport Protocol (FNTP) standardized in ISO 29281-1;
[15]
— IEEE WAVE Short Message Protocol (WSMP) standardized in IEEE 1609.3 ,
— ISO Fast Service Advertisement Protocol (FSAP) standardized in ISO 24102-5,
[15]
— IEEE WAVE Service Advertisement (WSA) standardized in IEEE 1609.3 ,

where ISO considered the architectural context of an ITS station specified in ISO 21217:2014, and IEEE

[13]
considered the architectural context of a WAVE device specified in IEEE 1609.0 .

Although initial versions of these protocols from ISO and IEEE are very similar, there are differences

in details of the message formats and the functionality. These differences were identified by the EU/US

[20]

task force HTG 3, from which a recommendation resulted to harmonize the protocols .

The result of harmonization of FNTP with WSMP, and of FSAP with WSA is presented in this document,

distinguishing interoperability modes, and enhanced features specified in this document.

With reference to this document, the initial editions of ISO 29281-1 and IEEE 1609.3 were revised, and

ISO 24102-5 was converted into EN ISO 22418, enabling global interoperability of equipment designed

for different architectures. Finally, ETSI developed EN 302 890-1 (a further service announcement

protocol profile) with reference to the previous edition of this document, i.e. ISO/TS 16460:2016.

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INTERNATIONAL STANDARD ISO 16460:2021(E)
Intelligent transport systems — Localized communications
— Communication protocol messages for global usage
1 Scope
This document specifies:

— the Localized Message (LM) format: an NPDU of a networking & transport layer protocol that does

not support routing of a packet through a network;

— the Service Advertisement Message (SAM): an APDU to be transported in an LM, for example;

— the Service Response Message (SRM): an APDU acknowledging a SAM that offered a service based

[2]
on an ITS application class to be transported in an LM, for example;
— related basic requirements for procedures.
Specifications are partly done by normative references to IEEE 1609.3(TM)-2016.

NOTE These message format specifications and basic procedures need to be complemented by complete

procedures and SAP specifications according to the context of usage, i.e. an ITS station specified in ISO 21217, or

[13]
a WAVE device specified in IEEE 1609.0 or any other context.
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/IEC 8824-1, Information technology — Abstract Syntax Notation One (ASN.1): Specification of basic

notation

IEEE 1609.3(TM)-2016: Standard for Wireless Access in Vehicular Environments (WAVE) — Networking

Services
3 Terms and definitions
No terms and definitions are listed in this document.

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/
4 Symbols and abbreviated terms
CIP communication interface parameter
C-ITS cooperative ITS
DNS domain name server
EIRP effective isotropic radiated power
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ISO 16460:2021(E)
ESAP ETSI Service Announcement Protocol
FNTP Fast Networking & Transport Protocol
FSAP Fast Service Advertisement Protocol
HTG Harmonization Task Group
IPv6 Internet Protocol version 6
ITS Intelligent Transport Systems
ITS-AID ITS application identifier
ITS-PN ITS port number
LM localized message
LPP Local Port Protocol
MAC medium access control
NPDU network protocol data unit
OER octet encoding rules
OSI open system interconnection
PSID provider service identifier
RX CIP receiver CIP
SAM service advertisement message
SAM-ID SAM identifier
SAM-Count SAM change of content identifier
SAP service access point
SRM service response message
TCP transmission control protocol
TPID transport protocol identifier
TX CIP transmitter CIP
UPER unaligned packet encoding rules
VANET vehicular ad-hoc network
WAVE wireless access in vehicular environment
WSA WAVE service advertisement
WSMP WAVE short message protocol
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ISO 16460:2021(E)
5 Localized communications messages
5.1 Purpose

Localized communication is used to communicate with nearby peer stations, e.g. ITS station units or

WAVE devices. These stations are uniquely identified with an OSI data link layer address, typically

by the MAC address. Networking in the sense of IP networking, where stations route packets to other

nodes through a network (cloud), is not supported. Nevertheless, multi-hopping can be performed in

different ways, e.g.:

— N-hop broadcast or N-hop multicast, which requires careful means to avoid flooding of the

communication channel;
[4]

— dedicated forwarding performed at higher layers, e.g. at the ITS-S facilities layer of an ITS station ;

this is a feature useful for geo-dissemination of information,

which create so-called "Vehicular Ad-hoc NETworks" (VANETs). Routing of packets through a network

in ITS will use the Internet protocol version 6 (IPv6).
5.2 Localized message protocol

As this document does not specify a specific localized communications protocol but just the structure

of messages of such protocols and related basic requirements, a hypothetical localized communications

protocol with the name "Localized Message Protocol" is used to simplify reading of the document.

5.3 Message formats

Figure 1 illustrates the basic format of the LM. Unaligned packet encoding rules UPER applied to the

ASN.1 type LMnpdu defined in A.2.1 result in the intended binary presentation of this LM format.

Figure 1 — General format of the LM NPDU

NOTE 1 In Figure 1 the "TPID" field (specified in IEEE 1609.3(TM)-2016 as a 1-octet unsigned Integer field

completely allocated in the WSMP-N-Header) is split into a "Feature selector" field of the "N-Header" and a

"T-Extensions flag" field of the "T-Header" (according to the general rules of the OSI model). However, the two

presentations result in identical binary presentations.
The LM consists of three parts:
— "N-Header"

— A 4-bit unsigned Integer "Subtype" number in the range of 0 to 15 indicating a networking

related feature.
— A 1-bit "N-Extensions flag".

— A 3-bit unsigned Integer "Version" number in the range of 0 to 7 indicating the version of

the localized message protocol. In case a receiver does not support the version, the received

packet cannot be processed. The first version number used is three in accordance with

IEEE 1609.3(TM):2016.
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ISO 16460:2021(E)

NOTE 2 The format presented in Figure 1 is such that WAVE devices implementing version 2 of

[15]
WSMP can identify LMs as WSMP messages with version number 3 or higher.

— A networking related feature specified in 5.4 and selected by the value contained in the field

"Subtype".
— "N-Extensions" being present if the "N-Extensions flag" is set to '1'b.

— A 7-bit unsigned Integer in the range of 0 to 127, the " TPID - Feature selector", indicating content

in the "T-Header".
— "T-Header".
— A 1-bit "TPID - T-Extensions flag".

— A transport related feature specified in 5.5 and selected by the TPID - Feature selector value

contained in the "N-Header".
— "T-Extensions" being present if the "T-Extension flag" is set to '1'b.

— A one or two octet field indicating the number of octets contained in "User data".

— Body.
— The "User data".

The distinction of "N-Header" (networking related features) and "T-Header" (transport related features)

is in line with the OSI layers 3 and 4; these two OSI layers constitute the ITS-S networking & transport

layer as illustrated in ISO 21217.

The field "Length of User data" has a length of one or two octets dependent on the value contained in it:

— One octet size: Values from 0 through 127. The most significant bit is always set to zero. Presentation

as 0x00 (=0) through 0xEF (=127), i.e. the remaining 7 bits contain an unsigned integer number.

— Two octet size: Values from 128 through 16383. The most significant bit of the first octet is

always set to one, and the second most significant bit of the first octet is always set to zero.

Presentation as 0x8080 (=128) through 0xBFFF (=16383), i.e. the remaining 14 bits contain an

unsigned integer number.

NOTE 3 This presentation results from the unaligned packed encoding rules applied to ASN.1 types of

unconstraint variable length.
5.4 Networking features
5.4.1 Subtype values

Networking features are identified by a Subtype value. Subtype values are presented in Table 1.

Table 1 — Subtype values
Subtype N-Extensions N-Extensions Networking related fea- Remark
flag tures
0 '0'b Not present Null-Networking Mandatory feature specified in
IEEE 1609.3(TM)-2016. Format
'1'b Present
specified in 5.4.2.
1 '0'b Not present ITS station-internal forwarding Format specified in 5.4.3.
'1'b Present
2 '0'b Not present N-hop forwarding Format specified in 5.4.4.
'1'b Present
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ISO 16460:2021(E)
Table 1 (continued)
Subtype N-Extensions N-Extensions Networking related fea- Remark
flag tures
3 '0'b Not present Geo-forwarding Reserved. Not specified in this
version of the Document.
'1'b Present
4 - 7 '0'b Not present Reserved for ISO Allows for further four networking
features.
'1'b Present
8 - 15 '0'b Not present Reserved for IEEE Allows for further eight networking
features.
'1'b Present
N-Extensions and related basic procedures shall be as specified in 5.4.5.

New networking features can be specified and linked to so far reserved Subtype values at a later stage

without breaking backward compatibility.
5.4.2 Networking feature 0
Subtype 0 selects the "Null-Networking" feature introduced in 5.4.1.

NOTE Procedures on how to use this feature in the context of an ITS station unit, or a WAVE device, or any

other context are outside the scope of this document.

The "Null-Networking" feature with Subtype 0 is the uppermost simple feature, as it requires only

processing of the TPID - Feature selector field specified in 5.6. Figure 2 presents the N-Header format

for Subtype 0 with N-Extensions being absent.
Figure 2 — N-Header for Subtype 0 without N-Extensions

Figure 3 presents the N-Header format for Subtype 0 with N-Extensions being present.

Figure 3 — N-Header for Subtype 0 with N-Extensions
N-Extensions and related basic procedures shall be as specified in 5.4.5.
5.4.3 Networking feature 1

Subtype 1 selects the "ITS Station-Internal Forwarding" feature introduced in 5.4.1.

NOTE Procedures on how to use this feature in the context of an ITS station unit, or a WAVE device, or any

other context are outside the scope of this document.

ITS station-internal forwarding is a feature applicable in ITS stations conformant with ISO 21218 (Link-

ID) and ISO 24102-4 (ITS-SCU-ID). It is used to forward packets between router units and host units that

are part of the same station/device. The field "Direction" contains an unsigned integer number with the

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ISO 16460:2021(E)

two possible values "0" ("from host to router") and "255" ("from router to host"). The field "Counter"

contains a 1-octet unsigned integer cyclic packet counter being unique in the unit that forwards a

packet. Figure 4 presents the N-Header format for Subtype 1 with N-Extensions being absent.

Figure 4 — N-Header for Subtype 1 without N-Extensions

Figure 5 presents the N-Header format for Subtype 1 with N-Extensions being present.

Figure 5 — N-Header for Subtype 1 with N-Extensions

NOTE In Figure 5, unlike in the presentation in Figure 1, subtype-specific elements (i.e. "Original

N-Header") are allocated between "N-Extensions" and "TPID - Feature Selector". This is to simplify processing

at the receiver side.
N-Extensions and related basic procedures shall be as specified in 5.4.5.
5.4.4 Networking feature 2
Subtype 2 select the "N-hop Forwarding" feature introduced in 5.4.1.

NOTE Procedures on how to use this feature in the context of an ITS station unit, or a WAVE device, or any

other context are outside the scope of this document.

N-hop forwarding is a feature that allows extending the communication range for information

dissemination (MAC broadcast or multicast mode) beyond the next directly reachable neighbour

stations. It uses parameters that allow flooding of the communication channel to be avoided. Figure 6

presents the N-Header format for Subtype 2 with N-Extensions being absent.
Figure 6 — N-Header for Subtype 2 without N-Extensions

The 22-bit Message ID is generated from a random number generator and is unique within the N-hop

communication range with a "high" likelihood. In case of duplicate Message ID values, forwarding might

not be performed correctly in a station.

The 2-bit unsigned Integer Hop Count indicates to a receiver whether a forwarding shall be performed

or not. If the Hop Count equals zero, forwarding is prohibited. Prior to forwarding of a packet, the Hop

Count shall be decremented by one. Consequently, a maximum of four hops is possible.

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ISO 16460:2021(E)

Forwarding shall be performed also if the TPID value contained in the received message is not supported

or is reserved.

Figure 7 presents the N-Header format for Subtype 2 with N-Extensions being present.

Figure 7 — N-Header for Subtype 2 with N-Extensions
N-Extensions and related procedures shall be as specified in 5.4.5.
5.4.5 N-Extensions

The structure of the N-Extensions is specified in Clause 7. Extension elements presented in Table 2 may

be used in the "N-Extensions" field.
Table 2 — N-Extensions elements
Element ID Element type (ASN.1) Element name
TXpower80211
c-TxPowerUsed80211= 4 Transmit Power Used (specified in
IEEE 1609.3(TM)-2016).
ChannelNumber80211
c-ChannelNumber80211 = 15 802.11 Channel Number used (specified in
IEEE 1609.3(TM)-2016).
DataRate80211
c-DataRate80211 = 16 802.11 Data Rate used (specified in
IEEE 1609.3(TM)-2016).
TXcip
c-LMtxCip = 80 Communication Interface transmit pa-
rameters.
RXcip
c-LMrxCip = 81 Communication Interface receive param-
eters (RX-CIP).
LMchannelBusyRatio
c-LMchannelBusyRatio = 82 Channel Busy Ratio.

The "Transmit Power Used" element is optionally included in the LM N-Header for use by the LM

[12]
recipient; see also IEEE Std 802.11 .

The "Channel Number" element is optionally included in the LM N-Header for use by the LM recipient;

[12]
see also IEEE Std 802.11 .

The "Data Rate" element is optionally included in the LM N-Header for use by the LM recipient; see also

[12]
IEEE Std 802.11 .

The "TX CIP" element is optionally included in the LM N-Header indicating CIP settings used by the

transmitter of the LM.

The "RX CIP" element is optionally included in the LM N-Header used with Subtype 1 indicating CIP

settings of the ITS-SCU that received the LM from a peer station.

The "Channel Busy Ratio" element is a one octet unsigned integer optionally included in the LM

N-Header reporting the observed channel busy ratio in percent (0 % up to 100 % in steps of 0,5 %). The

integer values 201 through 255 indicate "unknown ratio".
5.4.6 TPID values
Table 3 provides a summary of TPID values.
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ISO 16460:2021(E)
Table 3 — TPID values
TPID T-Extensions Transport related feature Remark
Feature T-Extensions
selector flag
0 '0'b Not present Information dissemination Mandatory feature specified in
IEEE 1609.3(TM)-2016. Format spec-
'1'b Present
ified in 5.5.1.
1 '0'b Not present General session mode Format specified in 5.5.2,
'1'b Present
2 '0'b Not present LPP mode Format specified in 5.5.3.
'1'b Present
3 - 10 '0'b Not present Reserved for ISO Allows fo
...

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