## 6 Results
### Management Overhead Characterization and Evaluation  
The three proposed privacy-aware modes are based on social metrics collected to calculate the trust metric. Mostly, the mobile nodes analyze their previous communications and extract the needed information (NCF, NEM) without gathering them. When the nodes obtain information directly by contacting their neighbors, they initiate a \"data collection\" process by sending requests and receiving responses from the other nodes, which induces an overhead to the network. To evaluate the \"data collection\" process, we defined simulation scenarios based on the protocols and movement models used in the previous experiments. We run privacy-aware routing in each scenario with a data collection process activated. We measure the following metrics: energy consumption, the average transmission time (ATT), and the overhead, which measures the average number of used packets for each node in the network during the \"data collection process\"--following the results organized by the movement model. Figure 16: The result of familiar mode with bus model. Random way movement model  
Figure 18 shows that the data collection process consumed a negligible amount of energy. The privacy-aware Epidemic routing consumes less than 0.05%, and the two others provide lower values. This result is expected since the \"data collection\" is a direct process of transferring packets to the final recipient. For the average transmission time for \"data collection\" packets per node, we see that the Epidemic routing protocol generates an average time of less than 2 s. In contrast, the Prophet protocol shows values around 0.5 s. The Spray and Wait protocol gives the highest values, with an ATT increasing with the network size from 0.5 to 4 s. Limiting the packet transmission to only direct transfer between nodes and saving the collected data locally to avoid sending new requests enabled the routers to retrieve needed data without causing a new delay. For the average number of packets used during the \"data collection\" process, the Spray and Wait protocol gives the lowest values (around five packets per node). The two other protocols increase on average from 5 to 500 packets per node. We can observe that, depending on the network size and the routing scheme, we need an average of less than (2 * size of the network) to ensure that all nodes have all the needed information. For example, using the Prophet protocol and 300 nodes in the network, we obtain an overhead  
Figure 17: The result of familiar mode with working day model. average of 500 packets per node. The average overhead registered is low and remains acceptable in the opportunistic networks. * Bus movement model  
Figure 19 shows the result of the data collection process evaluation using the bus movement model. The data collection process consumed more energy in this experiment than in the previous one. The Epidemic protocol reached 0.4%, the Prophet protocol 0.3%, and Spray and Wait registered the lowest value (under 0.1%). Those results confirm that the collection of relationship information did not consume high node energy. The registered values remain in the same interval as the previous movement model for the average transmission time. The ATT is less than 2 s for small-size networks for all used routing protocols. Then, it increases depending on the routing scheme, but still by less than 4 s. The results for packet overhead confirm the previous observations that routers use a small amount of packets to acquire the necessary information. On average, we need a number of operations close to the size of the network. * Working day movement model  
Figure 20 represents the evaluation of the collection process using the working day movement model with the three routing protocols. We observe that for all schemes, the impact of the collection process is very low. Unlike the previous movement models, the working day generates extreme conditions for message transfer. It defines a wide space and long duration.