## 6 Simulation Results
### HECTOR Results  
**Energy consumption overhead when VCost succeeds**. Figure 4 shows the ECO for paths provided by the different algorithms when VCost succeeds for a given source-destination pair. The energy overhead is drawn depending on the mean node degree and on the number of landmarks used to build \(V\) coordinates. We can see from this figure that HECTOR provides the lowest overhead within the protocols that guarantee delivery. We can see that the node degree and the number of landmarks have a limited impact on the performances of each protocol since the figure shows the energy overhead once a path has been found. Since the environment is homogeneous, the impact of these parameters is thus negligible on the path features. Figure 5 shows the same results in a topology with a hole, still when VCost succeeds. Here we can also see that the performances of HECTOR are the best within the protocols that guarantee delivery. Figure 4: ECO when VCost succeeds for \(3\) and \(5\) landmarks for a homogeneous topology. Figure 5: ECO when VCost succeeds for \(3\) and \(5\) landmarks for a topology with a hole. As expected, for each case, HECTOR provides a greater overhead than VCost. This is due to the routing process in HECTOR that tries to provide a progress in the tree at any step. Therefore, the tree root position is important for minimizing the energy consumption for a given source and destination, but it is not possible to have an optimal tree root position for all possible source-destination pairs. Nevertheless, as Figure 6 shows, the success rate of VCost is far from \(100\%\) and is not the same following the different scenarios. We can note that the more VCost succeeds, the more HECTOR is energy-efficient and sticks to VCost performances. This is because, in Algorithm 1, the \(V\) coordinates are chosen uppermost. On the other hand, the less VCost succeeds, the more HECTOR sticks to LTP performance. If VCost fails, that means that there is no path following \(V\) coordinates and thus HECTOR algorithm follows \(T\) labels to ensure packet delivery, as in LTP. This is also confirmed by results displayed by Figure 6 which are the percentage of times HECTOR progresses over \(V\) coordinates rather than only on \(T\) labels. This is correlated with the success rate of VCost which only follows \(V\) coordinates. Figure 6: Success rate of VCost routing algorithm (**a**) and number of times HECTOR follows \(V\) coordinates (**b**) for each scenario. Note that an exception occurs for low densities of HECTOR with \(3\) landmarks. This is due to, by construction and because of the low densities, the path followed by VCost can be far from the label root, which forces HECTOR not to follow the VCost coordinates but the LTP labels. This is less the case in topologies with holes because VCost coordinates also bypass the hole, which make the path followed by VCost closer to the root. This explains this phenomenon. We integrated this explanation in the revised version. **Energy consumption overhead when VCost fails. ** When VCost fails, HECTOR has to follow \(T\) labels to reach the destination. This feature is one of the main contributions of HECTOR and cannot be observed in Figures 4 and 5 since the latter ones show results for simulation runs where VCost succeeds. Therefore, Figures 7 and 8 draw the results of HECTOR, HECTOR' and LTP for every simulation run, about paths on which VCost fails. In Figures 7 and 8, HECTOR is the algorithm that provides the best performances regarding energy consumption, followed by HECTOR'. LTP, once again, is the least performing algorithm. Moreover, as expected, we can note that the global behavior of HECTOR and HECTOR' is the same as LTP's. As already mentioned, this is because, when there is no progress over \(V\) coordinates, HECTOR and HECTOR' follow the \(T\) labels, as LTP, and so on till reaching a node which can provide a progress regarding \(V\) coordinates. **Hop length. ** Figure 9 shows the mean hop length along the routing path for every algorithm.