# An Efficient Routing Protocol with Overload Control for Group Mobility in Delay-Tolerant Networking
## 4 Simulation Results  
The performance of the proposed protocol was analyzed through simulation using an opportunistic network environment (ONE) simulator [26; 27], which is one of the most widely used simulators for the DTN protocol--from the aspects of delivery ratio, overhead ratio, and delivery latency, as defined in Equations (8)-(10) as follows:  
\[Delivery\ ratio=\frac{No.of\ delivered\ messages}{No.of\ generated\ messages}. \tag{8}\]  
\[Overhead\ ratio=\frac{(No.of\ forwarded\ messages-No.of\ delivered\ messages)}{No.of\ delivered\ messages}, \tag{9}\]  
\[Delivery\ latency=\frac{Sum\ of\ latency\ of\ delivered\ messages}{No.of\ delivered\ messages}, \tag{10}\]  
Figure 4: Flowchart of the proposed protocol. Table 3 shows parameter values used in the simulation. In this paper, we consider a traffic scenario, where all messages generated at mobile nodes are delivered to a single mobile node, such as a mobile sink node in delay-tolerant wireless sensor networks [28], since in a battlefield environment, which is one of the main application areas of the proposed group mobility, it is likely that messages generated at mobile units of each group would be delivered to a single command center node. For performance comparison, we considered three comparable protocols in simulation. Table 4 compares the proposed protocol and three comparable protocols. In the individual DP protocol, forwarding conditions of the original PRoPHET protocol with individual delivery predictability were modified appropriately by using the forwarding conditions in Table 1 for fair comparison. Group DP protocol was the protocol proposed in our preliminary work [22]. Group DP + Reactive OC protocol is a combination of Group DP protocol [22] and the reactive overload control protocol, where overload control is enabled only when the message is delivered to a final destination node, as in [24]. Group DP + Proactive OC protocol is a combination of Group DP protocol and the proposed proactive overload control protocol, and we refer to this as the proposed protocol in numerical examples. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Protocol** & \multicolumn{1}{c}{**Forwarding Condition**} & **Overload Control** \\ \hline \multirow{6}{*}{Individual DP} & - & In Cases 1, 2, and 5, message is & \\  & forwarded to node \(y\) from node \(x\) if & \\  & \(P(y,z)>P(x,z)\). & & \\  & In Case 3, message is forwarded to node & No overload control \\  & \(y\) from node \(x\) if \(P(y,z)>T_{p}\). & \\  & In Case 4, message is forwarded to node & \\  & \(y\) from node \(x\) if \(P(y,z)>T_{r}\). & \\ \hline Group DP & Forwarding, as in Table 1 & No overload control \\ \hline Group DP + Reactive & \multirow{2}{*}{Forwarding, as in Table 1} & Forwarding is prohibited if a message is delivered to a destination node, and the delivered message to a destination node is removed from the buffer of the contact node. \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \cline{1-1}  & & \multicolumn{1}{c}{} \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of the proposed protocol with comparable protocols.