The increasing prominence of concepts such as Smart Production and Industrial Internet of Things (IIoT) within the context of Industry 4.0 has introduced a new set of requirements for the engineering of industrial systems, including support for dynamic environments, timeliness guarantees, support for heterogeneity, interoperability and reliability. These requirements are further exacerbated at the network level by the notable rise in the number and variety of devices involved. To stay competitive in this ever-changing industrial landscape while boosting productivity, it is vital to meet those requirements, combining established protocols with emerging technologies. Software-Defined Networking (SDN) is the forefront traffic management paradigm that offers flexibility for complex industrial networks, enabling efficient resource allocation and dynamic reconfiguration. Message Queuing Telemetry Transport (MQTT) is a low-overhead protocol of the application layer that is gaining popularity in the scope of the IoT and IIoT. However, its Quality-of-Service (QoS) policies do not support timeliness requirements. This article presents a framework that seamlessly integrates SDN and MQTT, enhancing network management flexibility while satisfying real-time requirements found in industrial environments. It leverages the User Properties of MQTTv5 to allow specifying real-time requirements. MQTT traffic is intercepted by a Network Manager that extracts real-time information and instructs an SDN controller to deploy corresponding network reservations. MQTT traffic across multiple edge networks is propagated by selected brokers using multicasting. Extensive experiments validate the proposed approach, demonstrating its superiority over MQTT and Direct Multicast-MQTT (DM-MQTT) DM-MQTT in latency reduction. A response time analysis, validated experimentally, emphasizes robust performance across metrics.

中文翻译：

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适用于工业应用的可扩展的基于 SDN 的实时 MQTT 框架

工业4.0背景下智能生产和工业物联网（IIoT）等概念的日益突出，为工业系统工程提出了一系列新的要求，包括对动态环境的支持、及时性保证、对异构性的支持、互操作性和可靠性。由于所涉及设备的数量和种类显着增加，这些要求在网络级别进一步加剧。为了在不断变化的工业格局中保持竞争力，同时提高生产力，将现有协议与新兴技术相结合来满足这些要求至关重要。软件定义网络 (SDN) 是最前沿的流量管理范例，为复杂的工业网络提供灵活性，实现高效的资源分配和动态重新配置。消息队列遥测传输 (MQTT) 是一种低开销的应用层协议，在物联网和工业物联网领域越来越受欢迎。然而，其服务质量（QoS）策略不支持及时性要求。本文提出了一个无缝集成 SDN 和 MQTT 的框架，增强网络管理灵活性，同时满足工业环境中的实时要求。它利用 MQTTv5 的用户属性来允许指定实时要求。 MQTT 流量由网络管理器拦截，网络管理器提取实时信息并指示 SDN 控制器部署相应的网络预留。跨多个边缘网络的 MQTT 流量由选定的代理使用多播传播。大量实验验证了所提出的方法，证明其在减少延迟方面优于 MQTT 和直接组播 MQTT (DM-MQTT) DM-MQTT。经过实验验证的响应时间分析强调了跨指标的稳健性能。