Intelligent transport systems -- Roadside modules SNMP data interface

Systèmes de transport intelligents -- Interface de données SNMP pour les modules en bord de route

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FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 20684-1
ISO/TC 204
Intelligent transport systems —
Secretariat: ANSI
Roadside modules SNMP data
Voting begins on:
2021-01-25 interface —
Voting terminates on:
Part 1:
2021-03-22
Overview
Systèmes de transport intelligents — Interface de données SNMP pour
les modules en bord de route —
Partie 1: Vue d'ensemble
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 20684-1:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2021
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ISO/FDIS 20684-1:2021(E)
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© ISO 2021

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ii © ISO 2021 – All rights reserved
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ISO/FDIS 20684-1:2021(E)
Contents Page

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

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

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

1.1 General ........................................................................................................................................................................................................... 1

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

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

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 Conformance ............................................................................................................................................................................................................. 3

6 Conventions ............................................................................................................................................................................................................... 5

6.1 ASN.1 ................................................................................................................................................................................................................ 5

6.2 SNMP terminology ............................................................................................................................................................................... 5

7 Architecture ............................................................................................................................................................................................................... 5

7.1 ITS services ................................................................................................................................................................................................ 5

7.2 Physical view ............................................................................................................................................................................................ 5

7.3 Communications view ...................................................................................................................................................................... 6

8 User needs ................................................................................................................................................................................................................... 6

9 Requirements .......................................................................................................................................................................................................... 7

9.1 Features ......................................................................................................................................................................................................... 7

9.2 Identifiable requirements.............................................................................................................................................................. 7

9.3 Structure of data exchange requirements ....................................................................................................................... 7

9.4 Agent performance requirements .......................................................................................................................................... 7

10 Dialogues ...................................................................................................................................................................................................................... 8

10.1 General dialogue rules ...................................................................................................................................................................... 8

10.1.1 Manager initiated ............................................................................................................................................................ 8

10.1.2 Generic and custom dialogues ............................................................................................................................. 8

10.2 Generic dialogues ................................................................................................................................................................................. 8

10.2.1 Get elemental data .......................................................................................................................................................... 8

10.2.2 Set elemental data .......................................................................................................................................................... 8

10.2.3 Get tabular data ................................................................................................................................................................ 8

10.2.4 Set tabular data ................................................................................................................................................................. 8

10.2.5 Get data column ................................................................................................................................................................ 9

10.2.6 Get data from dynamic table entry................................................................................................................... 9

10.2.7 Get row status of dynamic table entry .......................................................................................................... 9

10.2.8 Configure entry of a dynamic table .................................................................................................................. 9

10.2.9 Toggle active status of a dynamic table entry ......................................................................................10

10.2.10 Delete entry from a dynamic table ................................................................................................................10

11 Security........................................................................................................................................................................................................................10

11.1 Vulnerabilities .......................................................................................................................................................................................10

11.2 Authentication and access control ......................................................................................................................................11

11.3 Encryption ...............................................................................................................................................................................................11

11.4 Security recommendation ..........................................................................................................................................................11

Annex A (normative) Management information base (MIB) ....................................................................................................12

Annex B (normative) Requirements traceability matrix (RTM) ...........................................................................................19

Bibliography .............................................................................................................................................................................................................................20

© ISO 2021 – All rights reserved iii
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ISO/FDIS 20684-1:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

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

A list of all parts in the ISO 20684 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
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ISO/FDIS 20684-1:2021(E)
Introduction
0.1 Background

The need for standardized communication with ITS field devices is growing around the world. Several

countries have adopted SNMP-based field device communication standards.

There is a growing view and empirical evidence that standardizing this activity will result in improved

ITS performance, reduced cost, reduced deployment time, and improved maintainability. The ISO 20684

series extends ISO 15784-2 by defining the management information necessary to monitor, configure

and control features of field devices. The data elements defined in all parts of the ISO 20684 series may

be used with any relevant protocol, but were designed with an expectation that they would be used

with one of the ISO 15784-2 protocols.

By using this approach, agencies can specify open procurements and systems can be expanded

geographically in an open and non-proprietary manner, which reduces costs, speeds up deployment

and simplifies integration.
0.2 Overview

SNMP is a collection of well thought-out and well-proven concepts and principles. SNMP employs the

sound principles of abstraction and standardization. This has led to SNMP being widely accepted as the

prime choice for communication between management systems and devices on the internet and other

communications networks.

The original implementation of SNMP was used to manage network devices such as routers and

switches. Since then, the use of SNMP has grown into many areas of application on the internet and has

also been used successfully over various serial communications networks.

This document defines management information for ITS field devices following the SNMP conventions.

0.3 Document approach and layout
This document defines:

a) How conformance is defined in subsequent parts of the ISO 20684 series (Clause 5);

b) Terminology and symbols used throughout the various parts of the ISO 20684 series (Clause 3 and

Clause 4);

c) Conventions used throughout the various parts of the ISO 20684 series (Clause 6);

d) The ITS architectural services defined in ISO 14813-1 that are addressed by the ISO 20684 series

(Clause 7);

e) The rules used by other parts of the ISO 20684 series in defining the user needs that drive the

definition of requirements (Clause 8);

f) The rules used by other parts of the ISO 20684 series in defining requirements and constraints

(Clause 9);

g) A set of generic dialogues that are referenced by other parts of the ISO 20684 series (Clause 10);

h) A discussion of security that applies to all devices conforming to the ISO 20684 series (Clause 11);

i) The management information base (MIB) for the features defined by this document (Annex A );

j) A description of the requirements traceability matrix that is provided in each subsequent part of

the ISO 20684 series that traces defined requirements to the required design elements (Annex B).

© ISO 2021 – All rights reserved v
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 20684-1:2021(E)
Intelligent transport systems — Roadside modules SNMP
data interface —
Part 1:
Overview
1 Scope
1.1 General

Field devices are a key component in intelligent transport systems (ITS). Field devices include traffic

signals, message signs, weather stations, traffic sensors, roadside equipment for connected ITS (C-ITS)

environments, etc.

The ISO 20684 series defines data that can be used when field devices need to exchange information

with other external entities (called “managers” in this document, even if they are other field devices).

Field devices can be quite complex, necessitating the standardization of many data concepts for

exchange. As such, the ISO 20684 series is divided into several individual parts. This document (Part 1)

introduces the ISO 20684 series and provides normative content that applies to all subsequent parts.

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.

IETF RFC 2578, Structure of Management Information Version 2 (SMIv2), April 1999.

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
agent
entity (3.2) that can respond to get and set requests
3.2
entity
device or “thing” that becomes part of an intelligent transport system
3.3
event
information captured when a trigger (3.13) fires (3.6) within an agent (3.1)

Note 1 to entry: Events are often transmitted in notifications or stored in logs.

© ISO 2021 – All rights reserved 1
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ISO/FDIS 20684-1:2021(E)
3.4
exception

condition that creates an event (3.3) that a user can want to store in a log (3.7) or transmit in a

notification (3.9)
3.5
field device
fixed or portable roadside module that includes an agent (3.1)
3.6
fire
to start a process when a trigger (3.13) value transitions from false to true
3.7
log

registry of events (3.3) within an agent (3.1) that can be retrieved by a manager (3.8)

3.8
manager

entity (3.2) that can generate get and set requests and/or can receive report, trap, and/or other inform

messages
[SOURCE: ISO 15784-2:2015, 4.9 — modified]
3.9
notification

listing of one or more events (3.3) that the agent (3.1) can send to one or more managers (3.8)

3.10
response time

time from the receipt of the last byte of a Confirmed Class pduType to the start of the transmission of

the first byte of the response message (when access is allowed by lower layers)
3.11
target

entity (3.1) to which the field device (3.5) can need to send requests or notifications

Note 1 to entry: Field devices often need to send notifications to managers when triggers fire.

Note 2 to entry: Field devices can be configured to request data from other field devices to use in their expression

or trigger logic.

Note 3 to entry: Field devices can be configured to control other field devices in response to a trigger firing.

3.12
trap

notification (3.9) sent from an SNMP agent (3.1) to a SNMP manager (3.8) without an immediately

preceding request from the manager or any expectation of an acknowledgement
3.13
trigger
condition that evaluates to a Boolean value
4 Symbols and abbreviated terms
ASN.1 abstract syntax notation one
BER basic encoding rules
IAB Internet Architecture Board
2 © ISO 2021 – All rights reserved
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ISO/FDIS 20684-1:2021(E)
IP internet protocol
ITS intelligent transport systems
MIB management information base
OER octet encoding rules
OID object identifier
PDU protocol data unit
RFC request for comments
NOTE Specifically, RFCs published by the Internet Engineering Task Force
RTM requirements traceability matrix
SMIv2 structure of management information version 2
SNMP simple network management protocol
STD IAB standard
TLS transport layer security
UDP user datagram protocol
USM user-based security model
5 Conformance

Conformance to each part of the ISO 20684 series is defined as per the conformance section of each

part, which is written using the structure defined in this clause.

Conformance is driven by defined user needs. Each part of the ISO 20684 series may define user needs

and the design to fulfil the user need. User needs are written from the perspective of a manager for the

field device.

NOTE Some parts of the ISO 20684 series do not define any user needs, but only provide reusable design

elements that can be referenced by other parts of the ISO 20684 series.

Table 1 of each part of the ISO 20684 series (other than this document) identifies the user needs

associated with the part and indicates whether they are mandatory or optional for conformance to that

part. Each user need is also traced to a set of features. A feature is a high-level, architectural concept

that represents a coherent capability of the device that can support multiple user needs.

Table 2 of each part of the ISO 20684 series (other than this document) traces each feature to the

requirements for that feature.

Each user need, feature and requirement is identified by name and a reference. The reference can be

within the same part, a different part, or a different standard. When references are made to other

documents, all details and remaining traceability shall be defined in the referenced document.

Both tables indicate conformance for an item using one of the following conformance codes:

a) M – indicates the item is mandatory when an implementation claims conformance to its parent item.

b) O – indicates the item is optional when an implementation claims conformance to its parent item

and if no other parent item makes the item mandatory.
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ISO/FDIS 20684-1:2021(E)
Parent items are defined as follows:
a) The part is the parent item of each user need defined within it.

b) Each user need is a parent item for one or more features as shown by the indentation in Table 1. A

user need may trace to multiple features and a feature may trace from multiple user needs.

c) Each feature is a parent item for one or more requirements as shown by the indentation in Table 2.

A feature may trace to multiple requirements; a requirement may trace from multiple user needs

but typically only traces from one feature.

Note that a feature defined in one part of the ISO 20684 series can have a parent defined in another

part. Features should not be defined until at least one user need exists for the feature.

A qualifier may precede a conformance code. In such cases, the qualifier shall be a term followed by a

colon. The term shall be defined in Table 3 of each part as a reference to a specific clause in a specific

standard. The meaning of this notation is that the conformance code only applies when the referenced

clause is supported by an implementation.

EXAMPLE The code “condition:M” means that the indicated row is “mandatory” if the clause referenced by

the term “condition” is supported by the implementation.

An option group expression may follow the “O” conformance code. The option group expression is of

the form “. ()”, where group shall be a sequential number that groups a number of

options together and shall be a range of integers that indicate the number of options that

may be supported by an implementation from the option group.

EXAMPLE The code “O.2 (1..*)” means that the indicated row is optional, but one or more options from

option group 2 are to be supported.

The requirements referenced by Table 2 are written as “shall” statements. However, the “shall” only

applies if the conformance table indicates that the feature is required.

NOTE This document defines the rules to be followed by subsequent parts of the ISO 20684 series; it does

not define any user needs or features itself and therefore does not contain Tables 1-3.

Each requirement specifying a need for a data exchange shall trace to one dialogue and one or more

data elements that an implementation claiming conformance to the requirement shall support. The

traceability from requirements to dialogues and data elements shall be defined in a requirements

traceability matrix (RTM) contained in Annex B of each part of the ISO 20684 series. The RTM may

include references to dialogues and data elements defined in other documents; any locally defined

dialogues shall be defined in the body of the standard while all locally defined data elements shall be

defined in Annex A of the document using a management information base (MIB) conforming to the

format defined in IETF RFC 2578. If the implementation supports SNMP, all supported data element

instances (i.e. SNMP objects) shall be accessible via any dialogue that meets the requirements of SNMP

and the data element definition.

NOTE The dialogues defined in the ISO 20684 series are specified to promote a common interface for testing

purposes and are not intended to restrict otherwise allowable requests or notifications.

Annex A of this document defines a set of object identities (i.e. nodes on the OID tree) and textual

conventions (i.e. useful data types) that should be imported as needed by other MIB modules contained

in other parts of the ISO 20684 series.

As this document does not contain any user needs, the Annex B of this document does not contain an

RTM; however, it does provide additional requirements that shall be applicable related to the RTMs

contained in other parts of the ISO 20684 series.
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ISO/FDIS 20684-1:2021(E)
6 Conventions
6.1 ASN.1

This document contains MIBs, which are written in the form of ASN.1. This document also contains

references to and explanations of ASN.1 data concepts within its text. In all cases, the ASN.1 terms are

presented in a fixed width font (e.g. such as this) to distinguish these terms from normal English.

6.2 SNMP terminology

Terminology between the different versions of SNMP is slightly different. For the purposes of the

ISO 20684 series, the terminology of SNMPv3 is adopted.
7 Architecture
7.1 ITS services

The ISO 20684 series defines mechanisms by which ITS field devices can be monitored, configured and

controlled. ITS field devices may be used to support almost any ITS service, defined in ISO 14813-1,

with a roadside component.
7.2 Physical view

Figure 1 depicts the physical view of this interface using the graphical conventions defined by the

[19]

architecture reference for cooperative and intelligent transportation and also documented in

ISO 14813-5:2020, Annex B.
Figure 1 — Physical view of interface

The manager of the field device is shown in grey indicating that it can be any type of physical object,

such as a central system, another field device, a maintenance laptop or any other device that supports

the defined interface.

The field device is shown in orange, indicating that it is located in the field (e.g. along the roadside).

It shall have a connection to the manager and may have any number of connections to other ITS-S or

external systems.

The figure indicates two information transfers between these physical objects. The first is the

“configuration and commands” information flow from the manager to the field device. The second is

the “status and notifications” information flow from the field device to the manager. Both flows are

shown in green indicating that authentication is required and both are shown with a single arrowhead

indicating a unicast transfer.

Subsequent parts of the ISO 20684 series define needs, requirements and design details for various

field device capabilities.

NOTE This document is based on the use of SNMP, which implements a GET/SET paradigm where

there is a manager and an agent. However, a single field device entity can act as both a manager (e.g. sending

requests to other field devices) and as an agent (e.g. responding to requests from a centre or other field device)

simultaneously.
© ISO 2021 – All rights reserved 5
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ISO/FDIS 20684-1:2021(E)
7.3 Communications view

Figure 2 depicts how the ISO 20684 series is intended to relate to other standards using the ITS Station

architecture, as defined in ISO 21217.
Figure 2 — Typical communications stack

Parts 2-9 of the ISO 20684 series are reserved for features that are a part of the Management Plane of

an ITS Station. These standards do not define end-device functionality; rather they define management

services that may support end-device functionality. The management layer typically also supports

other data to manage the communications stack as defined by a variety of SNMPv3 MIBs.

Parts 10 and above of the ISO 20684 series will address the end-device functionality and are considered

part of the definition of ITS-S applications.

The information defined for the Management Plane and ITS-S applications can theoretically be

exchanged over any communications stack, but is designed to be exchanged using SNMPv3, as described

in ISO 15784-2, with certificate-based security using TLS for SNMP. SNMPv3 is typically exchanged

using well-known internet protocols, such as UDP/IP over any number of access layers to media.

8 User needs

Specific user needs are defined in subsequent parts of the ISO 20684 series. Each user need should be

written from the perspective of a manager and provide a definition with a justification for the need.

The definition of the user need may be followed with an explanation of how th
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