## 10 Conclusions  
We have shown that it is feasible to use SDN routing in IoT contexts for implementing data security requirements of secrecy, integrity, and conflicts, as we have defined them in Section 3. In the implementation method we propose, data are automatically labeled according to their source, and SDN routing tables will be constructed so that they will be forwarded only to entities meant to receive them; other data will be dropped. We have not explicitly mentioned the property of _availability_ in this paper; however, availability follows from the fact that every entity that is allowed to receive some data will receive it by the effect of SDN routing. Previous research [21, 36] has shown that, for any network, it is possible to efficiently calculate labels for the entities in such a way that data flows are determined by the label inclusion relationship. In this paper, it was shown how the labels can be used to construct forwarding tables for SDN controllers that will control data transfers, accordingly, thus ensuring data security. We have proposed a network organization based on cloud concepts with application entities and data entities (or servers, databases). We have demonstrated our method by using a simple 'hospital' example that was simulated using standard SDN simulation tools. We envisage future systems where security administrators will be able to configure secure data flows by composing graphs such as the ones presented in our figures at various levels of abstraction or granularity. Reconfigurations can also be done on such graphs, and labels and routing tables can be computed and updated automatically using our method. Routing is taken care of by external SDN routers that will not burden the IoT devices. The use of our method will not affect the normal execution of SDN, except for the mentioned recalculation of labels and routing tables when reconfigurations are done. Using our approach, it is possible to significantly enhance technologies like Google B4 WAN, Microsoft Azure, and the GENI testbed cited in Section 3.2 for implementing security requirements. With respect to the literature reviewed in Section 10, we note the following contributions to our work: Instead of using the lattice model, we use the partial order model, applicable to any network; we represent secrecy and integrity policies with a single mechanism, based on the use of a simple labeling method; we develop a generic SDN framework; we show how different data flows can be defined in a single network; we have methods for network reconfiguration; and finally, we have done an implementation and a simulation of our sample SDN-enabled network. It should be pointed out, however, that our approach is feasible only for networks where the centralized planning we have envisaged is possible. In more decentralized systems, SDN may not be feasible, and it may be necessary to use established methods based on encryption agreed upon among entities. And even in the case of centralized control, encryption may be necessary to protect from covert channels, since data are transmitted clearly. The combined use of our method with encryption will be the appropriate solution in most cases, depending on the organization of the network, its applications, and the expected security threats and risks. We leave these topics for future research. Furthermore, we have provided a generic method only, and we have shown how the general data flow could be organized. For the proposed method to become practical, it will require the creation of a suitable administrative model; this is the subject of our ongoing research. IoT networks can be very complex, and their design must take into consideration many different requirements, including security requirements that have not been considered here. **Author Contributions:** Conceptualization, A.S. and L.L. ; Methodology, A.S. and L.L. ; Validation, A.S.; Formal analysis, A.S. and L.L. ; Writing--original draft, A.S.; Writing--review & editing, A.S. and L.L. ; Supervision, L.L. ; Project administration, L.L.