Developments in Flexible Time-Triggered Switched Ethernet

The Flexible Time-Triggered Switched Ethernet (FTT-SE) protocol was proposed in 2006 [1] as a realization of the FTT paradigm [2] specifically adapted to switched Ethernet. This paradigm first appeared in 1998 implemented on CAN, the FTT-CAN protocol [3], followed by an implementation on shared Ethernet in 2002 [4]. The FTT paradigm is a framework to develop distributed real-time systems that are reconfigurable and adaptive. It has been successfully used for dynamic Quality-of-Service (QoS) management in control applications [5] and video transmission [6], and for dynamic reconfiguration of real-time systems [7] that are either open or include subsystems that operate occasionally. Essentially, it consists of carrying out time-triggered scheduling online in an open fashion, thus its name. To support prompt and consistent updates in the scheduling, FTT uses a master/multi-slave architecture where a master node schedules the traffic in Elementary Cycles (EC) and propagates the respective triggers through the system, using Trigger Messages (TM). The messages schedule for each cycle is called the ECSchedule and it is encoded in the respective TM. Upon receiving the TM, the slave (end) nodes transmit the messages indicated in the EC-Schedule. The flexibility of FTT goes well beyond the online scheduling of the time-triggered traffic. It also provides a framework that is amenable to combine different traffic classes. In particular, FTT protocols have typically supported synchronous (time-triggered) and asynchronous (eventtriggered) messages, each type within a dedicated window with a configurable bound, granting desired guaranteed bandwidths. In this talk we highlight recent FTT developments in the context of switched Ethernet technology. We start with FTTSE protocol basics and then provide a few lines on improving performance and robustness with the HaRTES switch that is an FTT-enabled Ethernet switch, as well as on improving scalability and dependability of FTT-SE/HaRTES systems.