Ethernet was not originally developed to meet the\udrequirements of real-time industrial automation systems and\udit was commonly considered unsuited for applications at the\udfield level. Hence, several techniques were developed to make\udthis protocol exhibit real-time behavior, some of them requiring\udspecialized hardware, others providing soft-real-time guarantees\udonly, or others achieving hard real-time guarantees with\uddifferent levels of bandwidth efficiency. More recently, there has\udbeen an effort to support quality-of-service (QoS) negotiation\udand enforcement but there is not yet an Ethernet-based data\udlink protocol capable of providing dynamic QoS management\udto further exploit the variable requirements of dynamic applications.\udThis paper presents the FTT-Ethernet protocol, which\udefficiently supports hard-real-time operation in a flexible way,\udseamlessly over shared or switched Ethernet. The FTT-Ethernet\udprotocol employs an efficient master/multislave transmission\udcontrol technique and combines online scheduling with online\udadmission control, to guarantee continued real-time operation\udunder dynamic communication requirements, together with data\udstructures and mechanisms that are tailored to support dynamic\udQoS management. The paper includes a sample application,\udaiming at the management of video streams, which highlights\udthe protocol’s ability to support dynamic QoS management with\udreal-time guarantees.
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