Description of BS ISO 15784-2:2015+A1:2020 2020

1.1 General

This part of ISO 15784 specifies a mechanism to exchange data and messages in the following cases:

1. between a traffic management centre(s) and roadside modules for traffic management;

2. between roadside modules used for traffic management.

The scope of this part of ISO 15784 does not include the communication between traffic management centre and in-vehicle units, between roadside modules and in-vehicle units, in-vehicle communication, in-cabinet communication, or motion video transmission from a camera or recorded media.

This part of ISO 15784 is complimentary to ISO 15784‑3, but uses a different application layer for the information exchanges to configure, control, and monitor the field traffic control roadside modules. Where ISO 15784‑3 is based on the DATEX standards, this part of ISO 15784 uses an alternative approach based on SNMP with an optional extension for more efficient transmission over low bandwidth media. Both of these standards conform to the application profile requirements set forth in ISO 15784‑1.

1.2 Overview

This application profile is suitable for usage when the following conditions apply:

1. when the data to be exchanged can be defined as one or more elements that can be retrieved or stored. The protocol can support a wide variety of devices and has adopted the concept of a management information base (MIB) which identifies the configuration, control, and monitoring parameters for the roadside module. This standardized approach is commonly used for network management applications for devices such as routers, switches, bridges, and firewalls. It is also used in many countries to control devices such as dynamic message signs;

2. when guaranteed, deterministic, real time exchange of data are not critical. SNMP operations are typically fairly fast, but the underlying network can cause delays in delivering messages or even lost messages; thus, the protocol is not appropriate for applications that require reliable sub-second communications;

3. for intermittent exchange of any defined data. Normal SNMP operations allow messages to be structured by combining any group of elements into a retrieval or storage request;

4. for repeated, frequent exchanges of the same message structure (with potentially different values) on even low bandwidth links. This profile supports both an efficient variant of SNMP known as STMP which allows the run-time definition of 13 messages that can be repeatedly exchanged as needed with minimal overhead;

5. for allowing a roadside module to issue exception reports when special conditions arise. This profile includes the concept of an inform message that allows an agent to notify the manager of special conditions even though the manager did not specifically request the information at the time.

Note that this part of ISO 15784 does not address the data required for each specific type of ITS device. Subsequent device communications standards are to be developed to identify the functionality of the device and the objects to manage and monitor that functionality. This part of ISO 15784 is similar to NTCIP 2301 that defines the protocols along with the objects required for controlling, operating, monitoring, and diagnosing those protocols. Other standards define device-specific objects. It is anticipated that regions will develop device MIB’s that meet their specific needs.

This part of ISO 15784 will allow for open systems deployment using devices from many manufacturers providing a variety of services in a shared network environment. With such open protocols, public MIB’s, and conformance to the standards, roadside modules can become interoperable among vendors and a variety of vendors can provide product in a systems environment.

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