# TSCH Multiflow Scheduling with QoS Guarantees:
## 4 Discussion and Conclusions  
In this paper, an analysis of the quality of service obtained by different TSCH schedulers has been carried out both by simulation and testbed. The schedules obtained with SDN WISE-TSCH allow resources to be classified with greater precision, by being able to fully distinguish traffic. This results in an end-to-end delay reduction of up to 70% compared to Orchestra. In addition, a 100% deadline satisfaction rate is achieved. In multiflow conditions where the network is saturated by traffic of different characteristics, it is the only protocol that can guarantee the requirements of each type of traffic independently. Due to control traffic and increased slotframe usage, SDN results in an increase in power consumption of 28%. SDN-based schedulers have a clear QoS orientation, where traffic engineering policies with higher complexity can be applied, obtaining satisfactory results in all cases.  
Schedullers such as Orchestra and MSF have the great advantage of being easy to deploy as they do not require any external intervention and all reconfiguration processes are performed locally. Their performance is good for non-critical applications. However, this performance is only achieved under low saturation conditions, when monitoring type flows are used. Moreover, in an environment with multiple information flows, they do not allow each of the flows to be guaranteed independently, resulting in increased delays and packet inter-arrival time. This moves them away from a deterministic behaviour, which is necessary in industrial environments, where each of the quality of service requirements must be guaranteed independently.  
Centralised schedulers, such as AMUS, also achieve high performance in PDR and end-to-end delay due to optimised schedules. However, they have high energy consumption and present difficulties in managing control traffic. This difficulty means that they have a high variation in PIAT at the same level as distributed ones, which reduces their determinism. This is due to the lack of integration between the different layers of the protocol stack, which leads to an inflexible operation, in which it is not possible to differentiate information flows.  
In summary, autonomous and distributed protocols are suitable for applications where simplicity rather than performance is required, as opposed to fully centralized protocols such as SDN, which aim for higher performance but have greater complexity. Logically, centralized protocols are an intermediate step between distributed and SDN, have the drawbacks of both and have no significant advantage.  
Conceptualization, VS.-P.; methodology, F.O.-S. In addition, V.S.-P.; investigation, F.O.-S., V.S.-P., T.A.-A. In addition, J.S.-B.; software, F.O.-S. In addition, T.A.-A.; validation, V.S.-P. In addition, J.S.-B.; writing--original draft preparation, F.O.-S. In addition, V.S.-P.; writing--review and editing, T.A.-A. In addition, J.S.-B.; super- vision, V.S.-P. In addition, J.S.-B. All authors have read and agreed to the published version of the manuscript.  
This work has been supported by DAIS ([[https://dais-project.eu/](https://dais-project.eu/)]([https://dais-project.eu/](https://dais-project.eu/))) which has received funding from the ECSEL Joint Undertaking (JU) under grant agreement No 101007273. The JU receives support from the European Union's Horizon 2020 research and innovation programme and Sweden, Spain, Portugal, Belgium, Germany, Slovenia, Czech Republic, Netherlands, Denmark, Norway and Turkey. It has also been funded by Generalitat Valenciana through the \"Instituto Valenciano de Competitividad Empresarial-IVACE\". Furthermore, has been supported by the MCyU (Spanish Ministry of Science and Universities) under the project ATLAS (PGC2018-094151-B-100), which is partially funded by AEI, FEDER and EU.  
Not applicable.  
The authors declare no conflict of interest.