ISO 29281-1:2018

Intelligent transport systems - Localized communications - Part 1: Fast networking & transport layer protocol (FNTP)

This document specifies the "Fast Networking & Transport Protocol" (FNTP) of the ITS-S networking & transport layer. FNTP is in support of efficient localized communications distinguishing networking related features and transport related features. FNTP is extendible in the future without breaking binary backward compatibility. This document specifies - message formats and related basic protocol procedures by reference to ISO TS 16460, and - further requirements for operation of FNTP in the context of an ITS station specified in ISO 21217.

Systèmes intelligents de transport — Communications localisées — Partie 1: Réseautique rapide et protocole de la couche transport

General Information

• Status: Published
• Publication Date: 17-Jun-2018
• ICS: 03.220.01 - Transport in general
• ICS: 35.240.60 - IT applications in transport
• Technical Committee: ISO/TC 204 - Intelligent transport systems
• Drafting Committee: ISO/TC 204/WG 16 - Communications
• Current Stage: 9060 - Close of review
• Completion Date: 02-Dec-2028

Relations

• Revises: ISO 29281-1:2013/Amd 1:2017 - Intelligent transport systems - Communication access for land mobiles (CALM) - Non-IP networking - Part 1: Fast networking & transport layer protocol (FNTP) - Amendment 1
• Effective Date: 05-Nov-2015
• Revises: ISO 29281-1:2013 - Intelligent transport systems - Communication access for land mobiles (CALM) - Non-IP networking - Part 1: Fast networking & transport layer protocol (FNTP)
• Effective Date: 05-Nov-2015

Overview

ISO 29281-1:2018 specifies the Fast Networking & Transport Protocol (FNTP) for localized communications in Intelligent Transport Systems (ITS). FNTP defines networking- and transport-layer behavior for ITS stations, including message formats (by reference to ISO/TS 16460) and operational rules when deployed in an ITS station context (per ISO 21217). The protocol is designed for efficient, localized V2X-style exchanges and is extendible without breaking binary backward compatibility.

Key technical topics and requirements

• Protocol architecture and communication principles: FNTP separates networking-related features from transport-related features and defines reference and implementation architectures.
• Message formats (FNTP NPDU): N-Header, TPID-FS modes and FNTP body are specified; the standard references ISO/TS 16460 for basic message structures and ASN.1 module definitions (Annex A/B).
• Service Access Points (SAPs): Defined SAPs include IN‑SAP, NF‑SAP, MN‑SAP, SN‑SAP to support layered interfacing between FNTP and ITS station services.
• TPID-FS modes: Multiple TPID-FS modes are defined (information dissemination, general session, LPP support) to support different transport behaviors.
• Forwarding and port management: Forwarding tables, CIP (Communication Interface Port) management, port allocation and maintenance procedures are specified for routers and hosts.
• Transmit/Receive procedures: Detailed TX/RX procedures for transport and network subtypes, including extension handling and error checks.
• Security and conformance: Secure communications considerations, conformance criteria, test methods and a Protocol Implementation Conformance Statement (PICS) proforma are included.
• Extensibility and compatibility: Designed to allow future extensions while preserving binary compatibility with deployed implementations.

Practical applications and who should use it

ISO 29281-1 (FNTP) is intended for practitioners building localized ITS communications systems:

• Vehicle OEMs and Tier‑1 suppliers implementing in‑vehicle ITS stacks
• Roadside unit (RSU) manufacturers and roadside infrastructure operators
• System integrators deploying cooperative ITS (C‑ITS) and localized traffic services
• Software developers implementing transport/network layers for ITS stations
• Testing labs and certification bodies validating FNTP conformance Use cases include localized V2V, V2I message exchange, traffic signal coordination and other ITS services that require efficient, reliable localized transport and forwarding.

Related standards

• ISO/TS 16460 - referenced for FNTP message formats and ASN.1 modules
• ISO 21217 - ITS station architecture and operational context
• Other parts of the ISO 29281 series and ITS networking standards may provide complementary specifications for deployment and system integration.

Keywords: ISO 29281-1, FNTP, Fast Networking & Transport Protocol, intelligent transport systems, localized communications, ITS networking, message formats, TPID-FS, forwarding tables, NF-SAP.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 29281-1
Second edition
2018-06
Intelligent transport systems —
Localized communications —
Part 1:
Fast networking & transport layer
protocol (FNTP)
Systèmes intelligents de transport — Communications localisées —
Partie 1: Réseautique rapide et protocole de la couche transport
Reference number
©
ISO 2018
© ISO 2018
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
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 General requirements . 2
6 Architectures . 3
6.1 General context and purpose of FNTP . 3
6.2 FNTP reference architecture . 4
6.3 Communication principles. 5
6.3.1 Transmission . 5
6.3.2 Reception . 5
6.3.3 FNTP ITS-PNs . 5
6.4 Implementation architectures . 6
7 Protocol elements . 6
7.1 Service access points . 6
7.1.1 IN-SAP . 6
7.1.2 NF-SAP . 6
7.1.3 MN-SAP . 6
7.1.4 SN-SAP . 6
7.2 FNTP NPDU . 7
7.2.1 General. 7
7.2.2 Subtype zero . 7
7.2.3 Subtype one . 7
7.2.4 Subtype two . 7
7.2.5 N-Extensions . 7
7.2.6 TPID-FS field . 8
7.2.7 TPID-FS zero - information dissemination mode . 8
7.2.8 TPID-FS one - general session mode . 8
7.2.9 TPID-FS two - LPP support mode . 8
7.2.10 T-Extensions. 8
7.2.11 FNTP body . 9
7.3 Secure communications . 9
7.4 Protocol management elements . 9
7.4.1 ITS-AID look-up table. 9
7.4.2 Service look-up table . 9
7.4.3 Forwarding table.10
8 General protocol procedures .11
8.1 Port management .11
8.2 Maintenance of entries in forwarding tables .11
8.3 Notification of changes in forwarding tables .11
8.4 Initial settings of forwarding tables in ITS-S hosts .12
8.4.1 Allocation and deletion of a port.12
8.4.2 Assignment of communication interfaces .12
8.5 Initial settings of forwarding tables in ITS-S routers .12
8.6 CIP management.13
8.6.1 Purpose of CIPs and basic procedures .13
8.6.2 Forwarding of TX-CIPs from ITS-S host to ITS-S router .13
8.6.3 Forwarding of CIPs from ITS-S router to ITS-S host .14
9 Transmitting packets procedures .14
9.1 General .14
9.2 NF-SAP transmission request .16
9.3 Transport related TX procedures.17
9.3.1 TPID-FS zero TX procedure .17
9.3.2 TPID-FS one TX procedure .17
9.3.3 TPID-FS two TX procedure .17
9.3.4 T-Extensions TX procedures .17
9.4 Network related TX procedures .18
9.4.1 Subtype zero TX procedure .18
9.4.2 Subtype one TX procedure .18
9.4.3 Subtype two TX procedure .19
9.4.4 N-Extensions TX procedures .19
9.5 Send request procedure .20
9.6 Subtype one forwarding from router to host TX procedure .21
10 Receiving packets procedures .21
10.1 General .21
10.2 Checking of FNTP N-Header .23
10.3 Network related RX procedures .23
10.3.1 Subtype zero RX procedure .23
10.3.2 Subtype one RX procedure .23
10.3.3 Subtype two RX procedure .24
10.3.4 N-Extensions RX procedures .24
10.3.5 TPID-FS checking .25
10.3.6 ITS-SFS check and forwarding table update .25
10.4 Transport related RX procedures .26
10.4.1 TPID-FS zero RX procedure .26
10.4.2 TPID-FS one RX procedure . .26
10.4.3 TPID-FS two RX procedure .26
10.4.4 T-Extension RX procedures.27
11 NF-SAP services .27
11.1 Overview .27
11.2 General NF-SAP services .27
11.3 NF-FNTP-PORT .28
11.3.1 NF-FNTP-PORT.request .28
11.3.2 NF-FNTP-PORT.confirm .29
11.4 NF-FNTP-COMM .29
11.4.1 NF-FNTP-COMM.request .29
11.4.2 NF-FNTP-COMM.confirm .30
11.4.3 NF-FNTP-COMM.indication .31
12 Dynamic data .32
13 Conformance .32
14 Test methods .32
Annex A (normative) ASN.1 modules .33
Annex B (informative) ASN.1 modules from ISO 16460 .40
Annex C (normative) Protocol Implementation Conformance Statement proforma .42
Annex D (normative) Path and flow management support .53
Bibliography .54
iv © ISO 2018 – 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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
This second edition cancels and replaces the first edition (ISO 29281-1:2013), which has been technically
revised. It also incorporates the Amendment ISO 29281-1:2013/Amd1: 2017.
The main changes compared to the previous edition are as follows:
— a complete technical revision in support of the common message format specified in ISO TS 16460
that is harmonized with IEEE WAVE;
— ASN.1 has been aligned with latest developments in ISO TC 204;
— provisioning for path and flow management has been added;
— normative annex related to conformance testing, that contains the PICS proforma, has been added.
A list of all parts in the ISO 29281 series can be found on the ISO website.
Introduction
This document is part of a family of International Standards for communications in Intelligent Transport
Systems (ITS) based on the ITS station and communication architecture specified in ISO 21217.
This document is Part 1 of a multipart standard which determines the "Intelligent Transport Systems"
(ITS) localized communications.
The FAST Networking & Transport layer Protocol (FNTP) is a protocol for localized communications.
FNTP comprises
— a basic port mapper protocol, used for localized communications between ITS station units (ITS-SUs),
— networking related protocol features for
— null-networking (single-hop communications),
— N-hop forwarding,
— ITS station-internal forwarding of packets between ITS station communication units (ITS-
SCUs) with ITS-S host role and ITS-S router role,
extendible with further features;
— transport related protocol features for
— information dissemination with ITS-AID as destination address,
— session support with ITS port numbers (ITS-PN) as source address and destination address,
— LPP,
extendible with further features.
The first version (2010) of FNTP was validated in the CVIS project of the European Commission.
Feedback from CVIS and other activities resulted in the second version (2013). This third version of
FNTP is the result of harmonization with the IEEE WAVE Short Message Protocol (WSMP); it is based on
the common message format specified in ISO TS 16460.
vi © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 29281-1:2018(E)
Intelligent transport systems — Localized
communications —
Part 1:
Fast networking & transport layer protocol (FNTP)
1 Scope
This document specifies the "Fast Networking & Transport Protocol" (FNTP) of the ITS-S networking &
transport layer.
FNTP is in support of efficient localized communications distinguishing networking related features
and transport related features. FNTP is extendible in the future without breaking binary backward
compatibility.
This document specifies
— message formats and related basic protocol procedures by reference to ISO TS 16460, and
— further requirements for operation of FNTP in the context of an ITS station specified in ISO 21217.
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 8825-2, Information technology — ASN.1 encoding rules: Specification of Packed Encoding Rules
(PER) — Part 2
ISO/TS 16460, Intelligent transport systems — Communications access for land mobiles (CALM) —
Communication protocol messages for global usage
ISO 17419, Intelligent Transport Systems — Cooperative systems — Classification and management of ITS
applications in a global context
ISO 21217, Intelligent transport systems — Communications access for land mobiles (CALM) — Architecture
ISO 21218, Intelligent transport systems — Hybrid communications — Access technology support
1)
ISO 24102-3 , Intelligent transport systems — ITS station management — Part 3: Service access points
2)
ISO 24102-4 , Intelligent transport systems — ITS station management — Part 4: Station-internal
management communications
ISO 24102-6, Intelligent transport systems — ITS station management — Part 6: Path and flow management
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21217 and the following apply.
1) 2nd edition to be published. Stage at time of publication: ISO/DIS 24102-3.
2) 2nd edition to be published. Stage at time of publication: ISO/DIS 24102-4.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
ITS-S facility layer service
process residing in the ITS-S facilities layer acting as source or destination of FNTP NPDUs
4 Abbreviated terms
FNTP Fast networking & transport protocol
ITS-PN ITS port number
ITS-S ITS station
ITS-SCU ITS station communication unit
ITS-SFS ITS-S facility layer services
ITS-SU ITS station unit
LM Localized message
TPID-FS Transport Protocol Identifier - Feature Selector
TPID Transport Protocol Identifier
NPDU Network Protocol Data Unit
UPER Unaligned Packed Encoding Rules
5 General requirements
All normative requirements related to the specification of the "Localized Message" (LM) in ISO TS 16460
shall be normative requirements in this document.
The Fast Networking & Transport layer Protocol (FNTP) specified in this document is a communications
protocol for the LM specified in ISO TS 16460. FNTP and the related LM format shall be identified in
FNTP network protocol data units (NPDUs) by the version number three.
The term LM NPDU in ISO TS 16460 is synonym with the term FNTP NPDU specified in this document.
The FNTP is identified at the ITS-S access layer by the Ethertype value 35,152 = 0x8950 published on [9].
An implementation supporting path and flow management shall be in accordance with ISO 24102-6.
An implementation for a distributed ITS-SU, i.e. an ITS-SU consisting of several ITS-SCUs interconnected
with an ITS station-internal network, shall be in accordance with ISO 24102-4.
The operational mode of subtype zero combined with TPID-FS zero, see 6.1, constitutes the
interoperability mode of an ITS station unit (ITS-SU) with an IEEE WAVE device compliant with
[17]
IEEE 1609.3 . In case of ITS-SUs that are declared to be interoperable with IEEE WAVE devices, this
mode shall be used for single-hop broadcast communications with no expected reply if the respective
value of ITS-AID as a destination address is registered at [11]. ITS-SUs that are not declared to be
interoperable with IEEE WAVE devices may also use TPID-FS one for such broadcast communication.
2 © ISO 2018 – All rights reserved

The binary presentation of the LM is given by the ASN.1 specification presented in A.2 applying
unaligned packet encoding rules (UPER).
As
[17]
— identical LM formats are used in FNTP and in WSMP specified in IEEE 1609.3 , and
[17]
— the features specifications in IEEE 1609.3 is a sub-set of the specification of FNTP,
an implementation of FNTP optionally may support the WAVE short messages from IEEE WAVE devices
by considering the following requirements for the interoperability mode:
1) The only supported access technology is IEEE 802.11 OCB mode specified in [18], which is given by
[3]
ISO 21215 with US frequency allocation and WAVE-specific details.
2) The applicable EtherType value of the WSMP is 35,036 = 0x88DC of WSMP published on [9].
3) The only mandatory operational mode in WAVE-conformant devices is WSMP with subtype zero
combined with TPID-FS zero.
NOTE Conformance tests for WSMP support are out of scope of this document.
6 Architectures
6.1 General context and purpose of FNTP
The FNTP specified in this document is designed as a protocol of the ITS-S networking & transport
layer of the ITS station (ITS-S) architecture recognizing the concept of the bounded, secured and
managed ITS-S specified in ISO 21217, and supporting the concept of ITS station communication
[5]
units (ITS-SCU) and various implementation features; see ISO 24102-1 (local station management),
[6]
ISO 24102-2 (remote station management), ISO 24102-3 (management and security service access
points), ISO 24102-4 (station-internal management communications), and ISO 24102-6 (path and flow
management).
FNTP is designed to enable localized communication between peer "ITS-S facility layer services"
(ITS-SFSs) in ITS station units (ITS-SUs) with minimum protocol overhead. ITS-SFS are sources and
destinations of FNTP NPDUs.
FNTP uses the LM format specified in ISO TS 16460, ISO TS 16460 specifies networking-related
protocol features and transport-related protocol features. Networking-related protocol features are
identified by means of a "Subtype" value. Transport-related protocol features are identified by means of
a "Transport Protocol Identifier - Feature Selector" (TPID-FS).
Networking-related features supported by FNTP are:
— Subtype 0: Null-networking;
— Subtype 1: ITS station-internal forwarding;
— Subtype 2: N-hop forwarding.
Optional functionality is supported by means of N-Extensions. N-Extensions are type-length-value
encoded data elements that contain networking-related information.
Transport-related features supported by FNTP are:
— TPID-FS 0: Information dissemination mode using ITS-AID as a destination port number;
— TPID-FS 1: General session mode using a destination ITS-PN and a source ITS-PN;
— TPID-FS 2: LPP mode.
Optional functionality is supported by means of T-Extensions. T-Extensions are type-length-value
encoded data elements that contain transport-related information.
For a given transmission to a peer ITS-SU exactly one networking-related feature (Subtype zero or
two) and one transport-related feature (TPID-FS zero, one, or two) is selected. For ITS station-internal
forwarding the Subtype one FNTP N-Header precedes a complete FNTP-NPDU.
NOTE DSRC application layer legacy systems support specified in [8] makes use of FNTP.
[3]
FNTP supports hybrid communications by supporting any kind of ad-hoc access technology, e.g. ITS-M5 ,
[2] [4]
IR , 60GHz . FNTP connects source and destination "endpoints" at the ITS-S facilities layers in peer
ITS stations, where these endpoints are identified by "ITS-Port Numbers" (ITS-PNs), and where peer ITS
station units are uniquely identified by a Link-ID of the access layer specified in ISO 21218. Consequently,
FNTP basically is a port mapper protocol. FNTP may also be used for information dissemination, where
an "ITS Application Identifier" (ITS-AID) takes the role of a destination port number.
6.2 FNTP reference architecture
Figure 1 illustrates the location of FNTP in the ITS station (ITS-S) specified in ISO 21217, and the
station-internal relations with other protocol entities.
Figure 1 — FNTP reference architecture
"Port management" of FNTP is specified in 8.1.
Management of FNTP is supported in general with a "CI Selection Management" initially introduced in
[5] [8]
ISO 24102-1 , with technical details of "Path and Flow Management" specified in ISO 24102-6 .
4 © ISO 2018 – All rights reserved

Other management approaches are also possible, e.g. within a different station architecture, as long as
interoperability based on the LM and on the functional protocol behaviour specified in this document
is ensured.
6.3 Communication principles
6.3.1 Transmission
Transmission requests may be presented by the ITS-S facilities layer via the NF-SAP. Sources of
messages in the ITS-S facilities layer are identified by ITS-PNs. Destinations of messages in the ITS-S
facilities layer are identified by ITS-PNs or by well-known registered ITS-AIDs, dependent on TPID-FS.
ITS-PNs may either be well-known registered numbers or dynamically assigned numbers. The registry
of ITS-PNs is at [11].
Well-known registered ITS-AIDs are mapped to locally assigned ITS-PNs (i.e. dynamically assigned ITS-
PNs - PORT_DYN, specified in ISO 17419) enabling a harmonized service access point towards the ITS-S
facilities layer that uses only ITS-PNs but no ITS-AIDs.
Valid transmission requests to a groupcast MAC address are given by a "well-known" destination
address (ITS-PN or ITS-AID) in combination with an existing groupcast VCI. The value of the source
address (ITS-PN), if used, is irrelevant with respect of validity of a transmission request in case no
reply is expected. Replies to groupcast messages are expected e.g. in case of the service advertisement
[7]
message specified in ISO 24102-5 .
Valid transmission requests to a unicast MAC address are given by any valid destination address in
combination with an existing unicast VCI. The value of the source address, if present, is irrelevant with
respect of validity of a transmission request in case no reply is expected.
Transmission requests are presented by the FNTP to the ITS-S access layer using services of the IN-SAP.
In implementations in accordance with ISO 24102-6, validity of a transmission request is given by a
valid ITS-S-FlowID.
6.3.2 Reception
Reception notifications are presented by the ITS-S access layer to the FNTP using services of the IN-SAP.
Sources and destinations of messages are identified by ITS-PNs contained in the FNTP NPDU. ITS-AIDs
used as destination address in FNTP NPDUs (TPID-FS = 0) are mapped to dynamically assigned ITS-PNs
enabling a harmonized service access point NF-SAP towards the ITS-S facilities layer.
Valid notified packets addressed to an ITS-PN are given by a known destination port address (ITS-PN).
Valid notified packets addressed to an ITS-AID are given by a known ITS-AID that is mapped to an ITS-
PN. Which CI was used for reception of the packet, and which is the source port address of the packet,
are not relevant for the validity of the packet, but are relevant for a potential reply.
Received packets indicating an FNTP version number that is not supported generally are invalid.
Notifications of received packets are presented by the FNTP to the ITS-S facilities layer using services
of the NF-SAP.
6.3.3 FNTP ITS-PNs
ITS port numbers (ITS PNs) are two octet unsigned Integer numbers of ASN.1 type PortNumber
specified in ISO 17419. ISO 17419 distinguishes well-known registered ITS-PNs (PORT_REG) and
dynamically assigned ITS-PNs (PORT_DYN), and presents initial number allocations for PORT_REGs.
NOTE Static well-known ITS-PN numbers and ITS-AIDs are assigned to ITS applications by a registration
authority; see ISO 17419. There are no dynamically assigned ITS-AIDs.
Dynamically assigned ITS-PNs (PORT_DYN) are unique only in the ITS-SCU that performed the
assignment. In distributed implementations specified in ISO 21217, i.e. ITS-SUs consisting of several ITS-
SCUs interconnected via an ITS station-internal network, always a pair of ITS-PNs are to be allocated,
i.e. one value assigned in an ITS-SCU with host role, and a corresponding value assigned in an ITS-SCU
with router role. This leads to the service look-up table specified in 7.4.2.
Allocation and deletion of dynamic and static well-known "ITS Port Numbers" (ITS-PNs) and ITS-AIDs
in an ITS station is specified 8.1.
6.4 Implementation architectures
FNTP supports the implementation architectures introduced in ISO 21217.
7 Protocol elements
7.1 Service access points
NOTE SAPs are functional descriptions which in many cases are not implemented as observable interfaces.
Thus in general SAPs are not testable. The requirements set up in this document with respect of SAPs thus just
mean the functional behaviour rather than a specific implementation. As far as related ASN.1 definitions are
given, these become mandatory as soon as the defined elements become observable, e.g. within a PDU for ITS
[7]
station-internal management communications specified in ISO 24102-4 .
7.1.1 IN-SAP
The FNTP interacts with the ITS-S access layer specified in ISO 21217 using service functionality of the
IN-SAP specified in ISO 21218.
The FNTP supports the IN-UNITDATA service functionality of the IN-SAP specified in ISO 21218.
The FNTP may support the IN-UNITDATA-STATUS and IN-UNITDATAACK service functionality of the
IN-SAP specified in ISO 21218.
NOTE Usage of the information given by the IN-UNITDATA-STATUS service is not specified in this document.
7.1.2 NF-SAP
The FNTP interacts with the ITS-S facilities layer specified in ISO 21217 offering service functionality
of the NF-SAP specified in Clause 11 and in A.2.
The FNTP provides the NF-FNTP-PORT service functionality and the NF-FNTP-COMM service
functionality of the NF-SAP specified in this document.
7.1.3 MN-SAP
The FNTP interacts with the ITS-S management entity specified in ISO 21217 using service functionality
of the MN-SAP specified in ISO 24102-3. This functionality is specified in A.3 by means of appropriate
ASN.1 type definitions.
7.1.4 SN-SAP
The FNTP may interact with the ITS-S management entity specified in ISO 21217 using service
functionality of the SN-SAP specified in ISO 24102-3. This functionality is specified in A.3 by means of
appropriate ASN.1 type definitions.
6 © ISO 2018 – All rights reserved

7.2 FNTP NPDU
7.2.1 General
The format of FNTP NPDUs is identical to the format of LM NPDUs specified in ISO TS 16460:2016, 5.3.
7.2.2 Subtype zero
Support of subtype zero specified in ISO TS 16460 (Null-Networking) is mandatory. This is the default
networking mode.
7.2.3 Subtype one
Support of subtype one specified in ISO TS 16460 is mandatory only in case an implementation supports
an ITS station-internal network interconnecting several ITS-SCUs. Subtype one is only used for ITS
station-internal forwarding of FNTP NPDUs. Usage of this subtype in links between peer ITS-SUs is
prohibited.
The field "ITS-SCU-ID ITS-S host" contains the ITS-SCU-ID of the ITS-S host. ITS-SCU-ID is specified in
ISO 24102-4, with its ASN.1 type ITS-scuId specified in ISO 17419.
The field "Link-ID VCI in ITS-S router" contains the Link-ID of the VCI in these ITS-S router. The format
of Link-ID is specified in ISO 21218.
Usage of subtype one in the "Original N-Header" field is prohibited.
7.2.4 Subtype two
Support of subtype two specified in ISO TS 16460 is optional. Subtype two may be used to achieve
[1]
resilience or minimum communication distance specified in ISO 17423 . Subtype two is restricted
to broadcast or multicast dissemination of information disregard whether a reply is expected or not.
Subtype two may be requested either in the NF-FNTP-COMM.request service primitive by indicating
a Hop Count larger than zero, or by the ITS station management. The ITS station management may
require an upper limit of Hop Count smaller than or equal to the possible maximum value of three.
7.2.5 N-Extensions
Table 1 presents currently identified N-Extensions.
Table 1 — N-Extensions
Name Element ID Comment
[3]
Transmit Power Used 4 Applicable for the access technology specified in ISO 21215 .
[17]
Details specified in IEEE 1609.3 .
[3]
802.11 Channel Number used 15 Applicable for the access technology specified in ISO 21215 .
[17]
Details specified in IEEE 1609.3 .
[3]
802.11 Data Rate used 16 Applicable for the access technology specified in ISO 21215 .
[17]
Details specified in IEEE 1609.3 .
a
CIPs are constructed from I-Parameters specified in ISO 21218 and may depend on the ITS-S access technology selected
for communications. Further details of CIPs are outside the scope of this document.
Table 1 (continued)
Name Element ID Comment
a
Communication Interface receive 80 Generally applicable. Specified in ISO 21218 and in this document.
parameters (RX-CIP)
Used for Subtype one to notify communication interface
parameters in the ITS-SCU with router role related to the
received FNTP NPDU.
a
Communication Interface transmit 81 Generally applicable. Specified in ISO 21218 and in this document.
parameters (TX-CIP)
Used for Subtype one to request settings of communication
interface parameters in the ITS-SCU with router role.
Channel Busy Ratio 82 Generally applicable, e.g. for channel congestion algorithms.
Usage is not specified in this document.
a
CIPs are constructed from I-Parameters specified in ISO 21218 and may depend on the ITS-S access technology selected
for communications. Further details of CIPs are outside the scope of this document.
7.2.6 TPID-FS field
Details of the FNTP T-Header are selected by the value contained in the TPID-FS field of the FNTP
N-Header.
7.2.7 TPID-FS zero - information dissemination mode
Support of TPID-FS zero is mandatory for ITS-SUs that are declared to be interoperable with IEEE WAVE
devices. This "Information Dissemination Mode" is a transport mode of operation for transmission of
FNTP NPDUs to multiple receivers (broadcast mode or multicast mode) if no reply is expected, and if
the ITS-SFS identified by an ITS-AID uses only a single transport layer port.
NOTE ITS-SUs that are not declared to be interoperable with IEEE WAVE devices can use TPID-FS one for
dissemination of information (broadcasting of information).
7.2.8 TPID-FS one - general session mode
Support of TPID-FS one is mandatory. This "General Session Mode" is the default transport mode of
operation for transmission of FNTP NPDUs to a single receiver (unicast mode) and to multiple receivers
if a reply is expected. It is also used for transmission of FNTP NPDUs to multiple receivers if no reply is
expected, and the related ITS-SFS has several receive ports.
7.2.9 TPID-FS two - LPP support mode
Support of TPID-FS two is optional.
7.2.10 T-Extensions
Table 2 presents currently identified T-Extensions.
8 © ISO 2018 – All rights reserved

Table 2 — T-Extensions
Name Element ID Comment
Packet Identifier 83 The "Packet Identifier" element is optionally included in the LM T-Header to
identify uniquely a specific packet in a sequence of packets from a specific
transmitter.
A related procedure is not specified so far.
NOTE Support for resilience by FNTP (acknowledgement of messages) is being developed for a next version of
this document. This support for resilience will likely require FNTP management PDUs with source / destination
ITS-PNs set to the value zero. So far FNTP can support resilience by selecting the ISO 21218 IN_SAP service for
acknowledged MAC frames.
7.2.11 FNTP body
The FNTP body field contains the "User Data" part of an ITS-FPDU specified in ISO 21217. The length of
the "User Data" field expressed in multiples of octets is contained in the "Length of User Data" field of
the T-Header.
7.3 Secure communications
FNTP NPDUs basically are not secured, as security means typically are assumed to be applied at the
higher layers, e.g. ITS-S facilities layer o
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