智能交通系统 涉及路边模块通信的数据交换 第2部分：使用简单网络管理协议 (SNMP) 的中心到现场设备通信

[中文适用范围]： 本文件规定了在下列情况下交换数据和消息的机制：a) 交通管理中心与用于交通管理的 ITS 路边设备之间的交换；b) 用于交通管理的 ITS 路边设备之间的交换。本文件不适用于： — 交通管理中心与车载单元之间的通信； — ITS 路边设备与车载单元之间的通信； — 车载通信； — 机柜内通信； — 来自摄像机或记录媒体的运动视频传输。本文件适用于以下两种情况：1) 要交换的数据可以定义为一个或多个可以检索或存储的元素 - SNMP 可以支持各种各样的设备，并采用了管理信息库 (MIB) 的概念，该概念可识别 ITS 路边设备的配置、控制和监控参数。这种标准化方法通常用于路由器、交换机、网桥和防火墙等设备的网络管理应用。它还在许多地区用于控制动态信息标志等设备。 2) 保证、确定性、实时的数据交换并不重要——SNMP 操作通常需要少于 100 毫秒的时间，但是底层网络可能会导致消息传递出现数秒的延迟，甚至丢失消息；因此，SNMP 不适用于需要可靠的亚秒级通信的应用程序。本文档可用于： — 任何定义数据的间歇性交换（正常的 SNMP 操作允许通过将任何一组元素组合成检索或存储请求来构造消息）； — 即使在相对低带宽的链路上，也重复、频繁地交换相同的消息结构（可能具有不同的值）；注 1 ISO/TS 26048-1 中定义的动态对象功能可用于消除通常与 SNMP 通信相关的大量开销，使其更适合低带宽链路。 — 允许 ITS 路边设备在出现特殊情况时发出异常报告。1  注 2 异常报告使用 SNMP 通知与 ISO/TS 26048-1 中定义的通知管理功能结合使用。 [外文原描述]： This document specifies a mechanism for exchanging data and messages in the following cases: a) exchange between a traffic management centre and ITS roadside equipment for traffic management; b) exchange between ITS roadside equipment used for traffic management. This document is not applicable to: — communication between traffic management centres and in-vehicle units; — communication between ITS roadside equipment and in-vehicle units; — in-vehicle communication; — in-cabinet communication; — motion video transmission from a camera or recorded media. This document is suitable for use when both of the following conditions apply: 1) The data to be exchanged can be defined as one or more elements that can be retrieved or stored – SNMP 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 ITS roadside equipment. 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 regions to control devices such as dynamic message signs. 2) Guaranteed, deterministic, real-time exchange of data is not critical – SNMP operations typically require less than 100 ms, but the underlying network can cause multi-second delays in delivering messages or even lost messages; thus, SNMP is not intended for applications that require reliable sub-second communications. This document can be used 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); — repeated, frequent exchanges of the same message structure (with potentially different values), even on relatively low-bandwidth links; NOTE 1 The dynamic object feature, defined in ISO/TS 26048-1, can be used to eliminate a considerable amount of overhead that is normally associated with SNMP communications to make it more suitable for low-bandwidth links. — allowing ITS roadside equipment to issue exception reports when special conditions arise. NOTE 2 Exception reporting uses SNMP notifications in combination with the notification management features defined in ISO/TS 26048-1.