# DTN Trustworthiness for Permafrost Telemetry IoT Network
## 7 Discussion  
On the one hand, Figures 10-12 show that the levels of trustworthiness achieved are similar for all the studied transport protocols with low network load (left side of the mesh and cases with fewer sensor clusters). This fact seems reasonable because we already selected the most suitable and top-performance transport protocols to perform our tests, discarding those that do not adapt well in LFNs. We believe that if other transport protocols less suitable for this kind of network had been tested, the difference in the results would be more evident. However, (1) the levels of BBR and Verus are slightly lower than their competitors, and (2) Copa, Indigo, and EAATP share the highest \(STR\) values in the case of low network load, although the predominance of EAATP grows as the network load increases (the yellow mesh is more visible than the others). Figure 12: Trustworthiness mesh (consensus). Figure 13: Trustworthiness working domain requiring \(STR>0.7\). On the other hand, we can also see that the redundancy mode with social trustworthiness (Figure 11) is the most robust scenario, given that its \(STR\) decrease in high-load situations is less accentuated compared to the other cases (Figures 10 and 12), always maintaining \(STR\) values greater than 0.5. Furthermore, it is confirmed that, in general, as the probability of a node experiencing a Byzantine error decreases, the achieved \(STR\) values accordingly increase. From the trustworthiness working domain (Figure 13), we can see the aforementioned predominance of the EAATP. As mentioned in Section 5, the scenario intended to deploy in the next Antarctic campaign was the \"7 redundant sensors \(\times\) 8 sensor clusters\". Concretely, we can check that this case reaches the \(STR\) requirement of 0.7 for any \(Pb_{0}\) value. If we focus on this case, in Figure 13, we can see that the EAATP is the most trustworthy protocol except for the \(Pb_{0}\) = 1 \(\times\) 10\({}^{-1}\) and \(Pb_{0}\) = 8 \(\times\) 10\({}^{-2}\) cases, in which Copa performs better. Table 3 shows, in detail, the results for the \"7 redundant sensors \(\times\) 8 clusters\" case. For each protocol and each \(Pb_{0}\), we show the best \(STR\) achieved from the three possible operational modes (standard, social, and consensus). Although Copa, CUBIC, and EAATP have similar results, the latter can outperform Copa and CUBIC between 0.1% and 0.5% better in terms of \(STR\) in most cases, and also outperforms up to 7% more than its other competitors. These results confirm our hypothesis, i.e., using a particular transport protocol can directly affect the system's trustworthiness in our use case. We believe that the EAATP's superior trustworthiness is caused by the fact that it incorporates a fairness mechanism to share the network bandwidth, which reduces congestion and packet losses. Moreover, EAATP's congestion control tries to occupy the entire network bandwidth rapidly, and its mechanism to differentiate between random channel losses and congestion losses optimizes its achieved throughput in heavy congestion situations. These features give the EAATP a competitive advantage in terms of performance in our use case, where the DTN opportunistic scheme we use to send accumulated data during the night as a bulk data transfer congests the network. For these reasons, we decided to use the EAATP as the backbone network transport protocol for our IoT telemetry service that will be deployed in the field during the next Antarctic campaign. Moreover, we can identify which of the three modes best suits the different scenarios which may arise. In general, the standard mode obtains the highest \(STR\) values when there is no redundancy (1 \(\times\) N zone). If redundancy is applied, the consensus solution shows the highest levels of trustworthiness in most cases with a low network load. However, as mentioned before, when the network load increases, the social trustworthiness solution is more robust, achieving the highest \(STR\) values for those cases.