## 6 Evaluation and Experimental Results
### Energy Model
#### 6.4.4 Overall Energy Consumption Results Compared with HIP-Based Solutions in IoT  
Energy consumption is a decisive criterion for Wireless Sensor Networks in the context of IoT. In Section 6.2, we present the comparison of HIP DEX packets' sizes before and after  
\begin{table}
\begin{tabular}{c|c|c|c|c|c} \hline \hline
**Handshake** & \multicolumn{2}{c}{**1 Hop (m)**} & \multicolumn{2}{c}{**4 Hop (m)**} & \multicolumn{2}{c}{**8 Hop (m)**} \\ \hline
4 packets & 1.729 & 1.62 & 1.959 & 1.85 & 2.267 & 1.26 \\
6 packets & 2.11 & 1.95 & 2.456 & 2.3 & 2.916 & 2.76 \\
8 packets & 2.998 & 2.79 & 3.459 & 3.25 & 4.074 & 3.86 \\ \hline \hline \end{tabular}
\end{table}
Table 13: Handshake Energy Communication Costs. Orange: results calculated from [PERSON] et al. [9] and green: LC-DEX’s solution.  
Figure 14: Energy communication costs of HIP DEX handshake packets including the signaling packets (6 packets). (**a**): Calculation done according to results obtained in [9]. (**b**): Results obtained with LC-DEX.  
the LC-DEX proposed compression solution of HIP DEX packets. The compression has a direct impact on the computational and communications energy costs. Figures 14 and 15 represent both communication and computational costs of existing HIP solutions. From Figure 15, we remark that solutions that propose compression (C-HIP, CD-HIP, Slimfit, Bettoumi et al. and LC-DEX) reduce considerably the communication overhead. Figure 16 gives a comparison of the overall energy costs of LC-DEX with previous HIP solutions.  
[PERSON] et al., D-HIP, and CD-HIP solutions could be judged as costly energy communication overheads solutions. [PERSON] et al.'s solution proposes a distribution model based on an important amount of messages involved in the communication. Concerning CD-HIP, the implementation of HIP BEX with its heavy cryptographic primitives and also, the introduction of a third party in the distribution phase without the proposition of a strategy that minimizes the number of exchanged messages between the HIP peers and the third party. CD-HIP has a significant energy consumption that is against the poor capabilities of sensors of IoT networks. Accordingly, the total communication cost is necessary very high in the case of frequent HIP session establishments. In the LC-DEX solution, the combination of the header compression and the omission of two signaling messages (NOTIFY, CLOSE_ACK) of the most efficient bootstrapping candidate for constrained devices (HIP DEX), proves an excellent reduction in energy consumption. The introduction of a collaborator in the distribution model in LC-DEX takes into consideration the minimization of the number of exchanged messages between the collaborator and the  
Figure 16: Overall energy consumption.  
Figure 15: Computational and communication energetic costs of evaluated solutions in comparison with LC-DEX.  
HIP peers. In addition, the integration of the third party in LC-DEX has an important role in the alleviation of the scalar multiplication of ECDH cryptographic computation of HIP DEX. Hence, an important impact is the minimization of the HIP energy costs.