# Mail Man Ferry: A Novel Routing Protocol in Intermittently Connected Networks
## 5 Performance Evaluation
### Performance Results and Discussions  
In this part, simulated experiments were carried out to analyze the performance of the proposed technique compared to two early protocols in ICN, namely the Epidemic routing protocol and the Prophet routing protocol, with different percentages of nodes cooperating. Figure 4 shows the delivery probability of the three compared routing protocols: Epidemic, prophet, and Mail Man Ferry, when node cooperation is 100%. Note that 100% node cooperation means any node during a simulation agrees to carry messages from other encountered nodes to deliver them to their final destinations. Figure 4 shows that Epidemic outperforms Prophet and Mail Man Ferry protocols in such a case. The Epidemic method distributes the highest number of message copies, which helps the protocol achieve the best possible delivery probability of messages. Prophet limits the distribution of messages copied to encountered nodes that have a higher probability of meeting their final destinations. Further, Mail Man Ferry limits its distributed copies to nodes in the Mail Man Ferry paths. More message distributions in an intermittently connected network increase the delivery probability when the node buffer is sufficient. This explains the performance of Epidemic when node cooperation is 100%. The experiment was also conducted at a node cooperation of 75% (see Figure 5). Note that the Mail Man Ferry method was not largely affected by the decline in node cooperation because the existing nodes in the mail man paths are sufficient to deliver the copies of the messages needed. On the other hand, the delivery probabilities in Epidemic and Prophet decreased by 7% and 3%, respectively. This is because their distributed copies had decreased by 25% without a proper routing mechanism that reduces such a decline in node cooperation. This shows that Mail Man Ferry mechanisms, such as predefined ferry \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Transmit Rate & 250 KBps \\ \hline Transmit Range & 50 m \\ \hline Message Size & 50 KB \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation environment parameters. paths, are capable of maintaining best possible delivery probability compared to Epidemic and Prophet. Figure 6 presents the delivery probability of the three compared protocols when node cooperation is 50%. The Mail Man Ferry method maintains its best message delivery probability performance compared to Epidemic and Prophet. The Mail Man Ferry method outperforms the two protocols by 6%, and this percentage is expected to grow when node cooperation decreases. Note that Mail Man Ferry continues to outperform Epidemic and Prophet in delivery probability taking advantage of the node credit mechanism employed. Figure 4: Delivery probability of Mail Man Ferry against Epidemic and Prophet with 100% node cooperation. Figure 5: Delivery probability of Mail Man Ferry against Epidemic and Prophet with 75% node cooperation. Figure 7 shows the delivery probability of the three compared protocols when node cooperation is 25%. There are two important reads from Figure 7. First, the Mail Man Ferry method maintains similar performance when node cooperation is 50%. This result shows that Mail Man Ferry is an efficient method against failure under any circumstances. The other note is that Epidemic and Prophet continue to underperform in delivery probability as node cooperation declines. This is due to the employed message dissemination mechanism in Epidemic and Prophet, whereas nodes in both protocols are expecting full cooperation of the encountered nodes without the node credit concept that is employed in Mail Man Ferry. Figure 6: Delivery probability of Mail Man Ferry against Epidemic and Prophet with 50% node cooperation. Figure 7: Delivery probability of Mail Man Ferry against Epidemic and Prophet with 25% node cooperation. The above figures show higher efficiency of the Mail Man Ferry method compared to the other routing protocols in an intermittently connected network (Epidemic and Prophet).