## 2 Related Work  
While the TSN family of standards keeps growing, thanks to the efforts of the IEEE 802.1 Working Group, recent research has addressed aspects such as the support for RT traffic dynamically added to the network. In fact, in some automotive applications, new flows can be triggered during the system operation by an event, for instance, the connection of trailers to cars or trucks [30]. To deal with this problem, some bandwidth partitioning mechanisms able to accommodate new flows without affecting the temporal guarantees of the already existent ones were proposed [31]. Among the works dealing with RT event-driven traffic in automotive communications, the one in [32] proposed the introduction of a new traffic class, called the ED RT class, and new bandwidth configuration and management mechanisms to provide very low end-to-end delay to RT event-driven flows. ED traffic is also supported by the IEEE 802.1 Qcr-2020 [33] standard, which specifies the Asynchronous Traffic Shaping (ATS), i.e., a per-flow token-bucket shaping mechanism that can be used to transmit ED traffic. With the introduction of the TSN family of standards, many works addressed schedulability analysis and scheduling algorithms for traffic flows on time-sensitive networks [34; 35; 36; 37; 38; 39; 40]. The work in [41] proposed a heuristic scheduling approach for time-driven flows while the work in [42] presented a solution to statically schedule time-driven flows according to an EDF-based policy. Such approaches are helpful for offline configuration, but they do not support ED flows. To accommodate novel applications, and hence the introduction of additional flows during the network operation, the works in [30; 43] proposed the use of the Software-Defined Networking (SDN) paradigm [44; 45; 46], which (i) enables a flexible and easy resource allocation [47] thanks to the separation of the centralized control plane from the data plane, and (ii) allows to change the network configuration at run time through lightweight online scheduling [48; 49]. To cope with dynamic reconfiguration using the ATS, the work in [50] addresses a configuration technique for the main parameters of the ATS that have an influence on the communication latency. However, the configuration parameters need to be set at design time and their calculation is a complex task [51]. For this reason, the approach in [50] adopts a Satisfiability Modulo Theories (SMT) solver for the configuration. However, the ATS is not suitable for guaranteeing determinism to time-driven traffic flows. The works in [52; 53] propose tools for calculating schedules according to the IEEE 802.1 Qbv standard to handle both ST and BE traffic. The goal of both works is to schedule flows using a time-driven approach and calculate the schedule so as to improve the latency of BE flows. However, every time a new RT flow is added, the entire schedule has to be recalculated from scratch. The work in [54] combines the Cyclic Queuing and Forwarding defined in [27] with the support for scheduled traffic. The approach in [54] provides a flexible way to schedule periodic and aperiodic RT traffic, but it cannot be implemented on IEEE 802.1Q legacy devices, as the transmission queues are handled according to policies that are not supported by the standard [27]. The approach presented in [55], called E-TSN, uses the transmission gate mechanism defined in the IEEE802.1Q standard to create time-slotted transmissions. Some timeslots are reserved for ST transmissions, while other timeslots are shared among ED traffic flows. The approach in [55] allows for the transmission of both ED and ST traffic, but without RT guarantees for ED traffic. Moreover, as timeslots are reserved to the ED traffic, there is a potential bandwidth waste if there are no ED frames in the queue.