## 6 Evaluation and Experimental Results
### Energy Model  
We focus our evaluation on the energy consumption during the HIP DEX handshake execution. This evaluation is focused on computation and wireless communications over the whole authentication process. Energy costs regarding cryptographic operations are calculated based on transmission, reception, and listening. Several works do not consider the listening period on their evaluations. Nevertheless, we consider the listening delay has an important incidence on the total energy cost and should not be deduced from the energy cost calculation. Besides, each experiment test iterates 100 times to calculate the average energy consumption and computing latency. The measurements of energy consumption are accomplished by the knowledge of the transmission and listening parameters current in milliAmpere (mA) and time in millisecond (ms) [37]. For calculating the listening duration that takes one packet to be sent from one HIP peer to another, we assume that the collaborator 6 BR is one-hop neighboring the HIP-peers. We deduce that the listening time is considered as the latency time of a packet to be transmitted from one node to another, adding the elapsed delay to get the response. This important delay has an impact on the energy communication cost and, hence, on the overall handshake energy cost. This measurement are given on Section 6.4.1. At the end of this section, a comparison with previous HIP-based solutions is made regarding the computational and communication computational costs. To calculate the energy consumption in mJ, we use the following formula equation:  
\[\text{Energy (mJ)}=\text{Time}\times\text{Current}\times\text{Voltage}, \tag{1}\]  
where:  
* Time is the execution time (ms) for individual cryptographic operation (time elapsed in CPU operations);
* Current is obtained based on experimental results;
* Voltage is the nominal voltage = 4.8 V.  
In FIT IoT-LAB, we can add a monitoring profile in the sensor nodes to obtain the real energy consumption (voltage, current, and power) in real-time execution. As a result, we have obtained that the A8 node consumes only 4.8 V (theoretically, it is between 3 V and 6 V [38]). The CPU has a power less than 300 mW [39] and, as known that for calculating the power, we use this formula:  
\[\text{Power}=\text{Voltage}\times\text{Current}.\]  
The IoT-LAB A8-M3 as indicated by its name is equipped by the IoT-LAB M3 object. As a consequence, it uses the same features (sensors, actuators, radio chip) as the integrated M3 sensor. So, the current draw for CPU is about 62.5 mA as a maximal value in the ball level for A8-M3 nodes. The embedded M3 co-microcontroller consumes 42 mA (16 mA at full power, 14 mA for radio transmission, and 12 mA for radio reception). Therefore, the A8-M3 CPU consumes about 20.5 mA as a maximum value. So, the current consumption will be less than this value. In our set of experiments, we randomly chose sensor nodes and implement a Constant Bit Rate (CBR) model equal to 250 kb/s. .4.1 Evaluation of the Multi-Hop Energy Communication Cost of the Proposed HIP DEX Compression Model  
We start our evaluation by calculating the energy gain of the proposed HIP DEX 6 LoWPAN compression header. Our experiments are executed under multi-hop architecture (1 hop, 4 hops, and 8 hops). Note that the distance between the HIP-peers and the 6 BR (CTTP) is 1 meter.