ISO/TS 20684-7:2022
(Main)Intelligent transport systems — Roadside modules SNMP data interface — Part 7: Support features
Intelligent transport systems — Roadside modules SNMP data interface — Part 7: Support features
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. Field devices often need to exchange information with other external entities (managers). Field devices can be quite complex, necessitating the standardization of many data concepts for exchange. As such, the ISO 20684 series is divided several individual parts. This document specifies user needs, requirements and design elements that are normatively used by other parts of the ISO 20684 series. Specifically, it defines an internal field device clock, a mechanism for grouping object values together to provide for more efficient transfer of data, and it provides formal requirements for the SNMP target and target parameters as defined in IETF RFC 3413. NOTE 1 There are similarities between certain portions of NTCIP 1103 and NTCIP 1201 and this document. NOTE 2 ISO 20684-1 provides additional details about how the ISO 20684 series relates to the overall ITS architecture.
Systèmes de transport intelligents — Interface de données SNMP pour les modules en bord de route — Partie 7: Service de support
General Information
Standards Content (Sample)
TECHNICAL ISO/TS
SPECIFICATION 20684-7
First edition
2022-10
Intelligent transport systems —
Roadside modules SNMP data
interface —
Part 7:
Support features
Systèmes de transport intelligents — Interface de données SNMP pour
les modules en bord de route —
Partie 7: Service de support
Reference number
ISO/TS 20684-7:2022(E)
© ISO 2022
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ISO/TS 20684-7:2022(E)
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ISO/TS 20684-7:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Conformance . 2
5 User needs . 4
5.1 Efficient exchange of data . 4
5.1.1 Object group user need . 4
6 Requirements . 4
6.1 Local clock . 4
6.1.1 Local clock definition . 4
6.1.2 Local clock data exchange requirements . 4
6.2 UTC clock . 4
6.2.1 UTC clock definition . 4
6.2.2 UTC clock data exchange requirements . 4
6.2.3 UTC clock capabilities . 5
6.3 Daylight saving time . 6
6.3.1 Daylight saving time definition . 6
6.3.2 Daylight saving time data exchange requirements . 6
6.3.3 Daylight saving time capability requirements . 7
6.4 Object group . 7
6.4.1 Object group definition . 7
6.4.2 Object group data exchange . 7
6.4.3 Object group capabilities . 8
6.5 SNMP target . 9
6.5.1 Target definition . 9
6.5.2 Target data exchange requirements . 9
6.5.3 Target capabilities . 9
6.6 SNMP target parameters . 10
6.6.1 SNMP target parameters definition . 10
6.6.2 SNMP target parameters data exchange requirements . 10
7 Dialogues .11
7.1 Retrieve a complex object group . 11
7.2 Set an object group value . 11
7.3 Clear an object group list . 12
8 Security vulnerabilities .12
Annex A (normative) Management information base (MIB) .13
Annex B (normative) Requirements traceability matrix (RTM) .37
Bibliography .43
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ISO/TS 20684-7:2022(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
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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
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expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 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.
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ISO/TS 20684-7:2022(E)
Introduction
0.1 Background
The need for standardized communication with ITS field devices is growing around the world.
Several countries have adopted Simple Network Management Protocol (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 ISO 20684 series may be
used with any 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) the conformance requirements for this document (Clause 4);
b) a set of user needs for user-defined trigger conditions that can “fire” to initiate actions (Clause 5);
c) a set of detailed requirements for the identified user needs (Clause 6);
d) custom dialogues for the logging feature (Clause 7);
e) security considerations for the information defined in this document (Clause 8);
f) the management information bases that define the data for the defined requirements (Annex A);
g) the requirements traceability matrix (RTM) that traces the requirements to the design elements
(Annex B).
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TECHNICAL SPECIFICATION ISO/TS 20684-7:2022(E)
Intelligent transport systems — Roadside modules SNMP
data interface —
Part 7:
Support features
1 Scope
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.
Field devices often need to exchange information with other external entities (managers). Field devices
can be quite complex, necessitating the standardization of many data concepts for exchange. As such,
the ISO 20684 series is divided several individual parts.
This document specifies user needs, requirements and design elements that are normatively used by
other parts of the ISO 20684 series. Specifically, it defines an internal field device clock, a mechanism
for grouping object values together to provide for more efficient transfer of data, and it provides formal
requirements for the SNMP target and target parameters as defined in IETF RFC 3413.
NOTE 1 There are similarities between certain portions of NTCIP 1103 and NTCIP 1201 and this document.
NOTE 2 ISO 20684-1 provides additional details about how the ISO 20684 series relates to the overall ITS
architecture.
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 8825-1, Information technology — ASN.1 encoding rules — Part 1: Specification of Basic Encoding
Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)
ISO/IEC 8825-7, Information technology — ASN.1 encoding rules — Part 7: Specification of Octet Encoding
Rules (OER)
ISO 20684-1:2021, Intelligent transport systems — Roadside modules SNMP data interface — Part 1:
Overview
IETF RFC 2578, Structure of Management Information Version 2 (SMIv2), April 1999.
IETF RFC 2579, Textual Conventions for SMIv2, April 1999.
IETF RFC 2580, Conformance Statements for SMIv2, April 1999.
IETF RFC 3411, An Architecture for Describing Simple Network Management Protocol (SNMP) Management
Frameworks, December 2002.
IETF RFC 3413, Simple Network Management Protocol (SNMP) Applications, December 2002.
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ISO/TS 20684-7:2022(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20684-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Conformance
This clause follows the rules defined in ISO 20684-1. Table 1 traces each user need to a set of software
features. Table 2 traces each feature to a set of requirements. Table 3 defines terms that are used as
predicates in the conformance codes listed in Tables 1 and 2. For a full understanding of these tables
and codes, see ISO 20684-1.
Table 1 — User need and feature conformance
Need Requirement Conformance
5.1: Efficient exchange of data O
6.4: Object group M
Table 2 — Requirement conformance
Feature Requirement Conformance
6.1: Local clock
6.1.2.1: Configure local clock M
6.1.2.2: Confirm local clock configuration M
6.1.2.3: Determine local clock time M
6.2: UTC clock
6.2.2.1: Discover UTC clock capabilities M
6.2.2.2: Configure UTC clock M
6.2.2.3: Confirm UTC clock configuration M
6.2.2.4: Determine UTC clock status M
6.2.2.5: Determine UTC time source status M
6.2.2.6: Set UTC time snmp_time:M
6.2.2.7: Retrieve UTC time M
6.2.2.8: Determine time discontinuity information M
6.2.3.1.1: Support for SNMP time configuration O.1 (1.*)
6.2.3.1.2: Support for network time protocol O.1 (1.*)
6.2.3.1.3: Support for radio time broadcast O.1 (1.*)
6.2.3.1.4: Support for satellite time signal O.1 (1.*)
6.2.3.2.1: Line frequency O.2 (1.*)
6.2.3.2.2: Crystal O.2 (1.*)
6.3: Daylight saving time
6.3.2.1: Determine daylight saving time capabilities M
6.3.2.2: Configure daylight savings schedule M
6.3.2.3: Confirm daylight savings schedule configuration M
6.3.2.4: Determine daylight savings time active M
6.3.2.5: Determine daylight savings time adjustment M
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ISO/TS 20684-7:2022(E)
TTabablele 2 2 ((ccoonnttiinnueuedd))
Feature Requirement Conformance
6.3.3.1: Number of daylight saving entries M
6.4: Object group
6.4.2.1: Determine object group capabilities M
6.4.2.2: Configure object group M
6.4.2.3: Confirm object group configuration M
6.4.2.4: Retrieve simple object group data M
6.4.2.5: Retrieve complex object group data O
6.4.2.6: Set new value for the object group set:M
6.4.2.7: Retrieve the last object group value set set:M
6.4.2.8: Retrieve object group statistics M
6.4.2.9: Clear object group M
6.4.2.10: Toggle object group M
6.4.2.11: Retrieve object group status M
6.4.3.1: Number of referenced objects M
6.4.3.2: Object group variable bindings size M
6.4.3.3: Object group basic encoding M
6.4.3.4: Object group octet encoding O
6.4.3.5: Support of set operations on object groups O
6.4.3.6: Support for complex object groups O
6.5: SNMP target
6.5.2.1: Configure a target M
6.5.2.2: Confirm a target configuration M
6.5.2.3: Delete a target configuration M
6.5.2.4: Toggle a target M
6.5.2.5: Retrieve target row status M
6.5.2.6: Retrieve target statistics M
6.5.3.1.1: Support for SNMPv1 targets O
6.5.3.1.2: Support for SNMPv2c targets O
6.5.3.1.3: Support for SNMPv3 targets M
6.5.3.1.4: Support for STMP targets O
6.5.3.2.1: Support for UDP/IP targets O
6.5.3.2.2: Support for TCP/IP targets O
6.5.3.2.3: Support for DTLS/IP targets M
6.5.3.2.4: Support for TLS/IP targets O
6.5.3.3: Security profiles M
6.6: SNMP target parameters
6.6.2.1: Configure SNMP target parameters M
6.6.2.2: Confirm configuration of SNMP target parameters M
6.6.2.3: Delete SNMP target parameters M
Table 3 — External standard reference
Predicate Clause
snmp_time 6.2.3.1.1
set 6.4.3.5
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ISO/TS 20684-7:2022(E)
5 User needs
5.1 Efficient exchange of data
5.1.1 Object group user need
It is not uncommon for an SNMP manager to perform requests on the same group of managed object
values from an SNMP agent multiple times. For example, an SNMP manager can potentially be configured
to request a specific group of objects periodically to monitor the status of a device or when a certain
set of predefined conditions occur. Normal SNMP operations require the complete object identifier
(OID) of every object value to be specified in each request. These OIDs are often 10-20 octets in length,
which can significantly increase communications overhead when the values being retrieved are small
(e.g. one-octet INTEGERs). This document defines a mechanism to allow a manager to configure object
groups, which can then be used to interact with multiple managed objects via a single OID.
6 Requirements
6.1 Local clock
6.1.1 Local clock definition
The local clock feature allows a field device to be aware of the local time as adjusted from the UTC clock
by the local time zone and any daylight saving algorithms in effect, if the daylight saving feature is
supported.
6.1.2 Local clock data exchange requirements
6.1.2.1 Configure local clock
The field device shall allow a manager to configure the local time zone for the clock.
6.1.2.2 Confirm local clock configuration
The field device shall allow a manager to confirm the configuration of the local clock.
6.1.2.3 Determine local clock time
The field device shall allow a manager to determine the local date and time.
6.2 UTC clock
6.2.1 UTC clock definition
The UTC clock feature allows a field device to maintain awareness of passing time; it represents the
UTC time within the field device. However, there is no formal requirement as to the exact time source or
accuracy. Ideally, it should be synchronized with a reliable and accurate time source in a secure manner.
6.2.2 UTC clock data exchange requirements
6.2.2.1 Discover UTC clock capabilities
The field device shall allow a manager to determine the capabilities of the UTC clock, including which
time source and time-keeping options are available.
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ISO/TS 20684-7:2022(E)
6.2.2.2 Configure UTC clock
The field device shall allow a manager to configure which available time source and time-keeping
option to use as well as the frequency for synchronizing the clock and when to report discontinuities in
time synchronization.
6.2.2.3 Confirm UTC clock configuration
The field device shall allow a manager to determine the configuration of the UTC clock.
6.2.2.4 Determine UTC clock status
The field device shall allow a manager to determine the time source and time-keeping option actually
being used and the last time the clock was synchronized with the configured time source.
6.2.2.5 Determine UTC time source status
The field device shall allow a manager to determine the status of each supported time source.
6.2.2.6 Set UTC time
If a field device supports the configured time capability of the UTC clock feature, the field device shall
allow a manager to set the current UTC time using SNMP.
NOTE This is perhaps the easiest time synchronization to implement, but also the least accurate. Variable
multi-second communication network delays can occur between the time the manager initiates the set operation
and the time the field device receives the command, especially when the command has to traverse a complex
communications network.
6.2.2.7 Retrieve UTC time
The field device shall allow a manager to retrieve the current time in UTC.
NOTE Variable multi-second communication network delays can occur between the field device transmitting
the time and the manager receiving it, especially when the command has to traverse a complex communications
network.
6.2.2.8 Determine time discontinuity information
The field device shall allow a manager to determine information about discontinuities in its UTC time to
enable to the detection of unusual behaviour in the clock.
NOTE The UTC time is expected to consistently increment its value. However, resynchronizing with an
outside time source can result in an adjustment, known as a discontinuity.
6.2.3 UTC clock capabilities
6.2.3.1 Time source
6.2.3.1.1 Support for SNMP time configuration
The field device shall allow a manager to configure the time by SNMP.
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ISO/TS 20684-7:2022(E)
6.2.3.1.2 Support for network time protocol
The field device allows the time to be set using the Network Time Protocol version 4 (NTPv4).
NOTE NTPv4 does not have any security. Devices that support NTPv4 are encouraged to provide mechanisms
to physically disable access to this protocol and thereby close a potential security threat for systems that choose
not to use this feature.
6.2.3.1.3 Support for radio time broadcast
The field device is able to set its time using a time signal broadcast over land-based radio waves.
6.2.3.1.4 Support for satellite time signal
The field device shall allow setting the time in the device based on satellite time signals.
6.2.3.2 Time-keeping
6.2.3.2.1 Line frequency
The field device shall allow time-keeping by monitoring the local electrical line frequency.
6.2.3.2.2 Crystal
The field device shall allow time-keeping with the use of an on-board time crystal.
6.3 Daylight saving time
6.3.1 Daylight saving time definition
The daylight saving time (DST) feature allows a manager to define when the local clock should spring
forward and fall backwards to conform to local time customs. In addition to defining when the events
occur, the design also allows the manager to specify how large of a shift is required. Finally, the design
allows for multi-stage daylight savings adjustments (e.g. spring a half hour forward and then spring
another half hour forward before falling back half an hour twice), but only requires support for a single
stage. A procurement specification can require support for multi-stage changes, if deemed necessary.
6.3.2 Daylight saving time data exchange requirements
6.3.2.1 Determine daylight saving time capabilities
The field device shall allow a manager to determine the number of daylight saving time event pairs that
the device supports.
NOTE A daylight saving time event pair consists of the spring forward and fall back events.
6.3.2.2 Configure daylight savings schedule
The field device shall allow a manager to configure the start and end times for daylight saving time as
well as the amount of time that the local time should shift.
6.3.2.3 Confirm daylight savings schedule configuration
The field device shall allow a manager to confirm the configuration of the daylight savings schedule.
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ISO/TS 20684-7:2022(E)
6.3.2.4 Determine daylight savings time active
The field device shall allow a manager to determine the status of each daylight savings time rule.
6.3.2.5 Determine daylight savings time adjustment
The field device shall allow a manager to determine the total of the current daylight savings time
adjustments.
6.3.3 Daylight saving time capability requirements
6.3.3.1 Number of daylight saving entries
If a field device supports the local clock feature, the field device shall support at least one annual
daylight saving adjustment.
6.4 Object group
6.4.1 Object group definition
An object group can minimize the amount of communications overhead for requests that will be
regularly repeated. Each object group value is a user-configured sequence of data elements from the
device. The data can be stored or retrieved without including the OID for each individual field within
the object group while also using the more efficient octet encoding rules (OER) rather than the normal
basic encoding rules.
6.4.2 Object group data exchange
6.4.2.1 Determine object group capabilities
6.4.2.2 Configure object group
A field device shall allow a manager to configure the objects to be contained within an object group.
6.4.2.3 Confirm object group configuration
A field device shall allow a manager to determine the configuration of an object group.
6.4.2.4 Retrieve simple object group data
A field device shall allow a manager to retrieve the values of each object within an object group through
a simple request.
6.4.2.5 Retrieve complex object group data
A field device shall allow a manager to retrieve the values of each object within an object group using a
two-step process, designed to prevent timeouts for requests that require significant processing time.
6.4.2.6 Set new value for the object group
A field device shall allow a manager to perform a set operation on the object group.
6.4.2.7 Retrieve the last object group value set
A field device shall allow a manager to retrieve the last value submitted in a set request for the object
group.
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6.4.2.8 Retrieve object group statistics
A field device shall allow a manager to retrieve statistics about when the last retrieval operation was
made and the estimated duration for requests.
6.4.2.9 Clear object group
The field device shall allow a manager to clear the definition of an object group.
6.4.2.10 Toggle object group
The field device shall allow a manager to enable/disable an object group.
6.4.2.11 Retrieve object group status
The field device shall allow a manager to retrieve the status of an object group.
6.4.3 Object group capabilities
6.4.3.1 Number of referenced objects
The field device shall support at least two referenced objects for each object group.
NOTE An object group only offers a si
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