# An Efficient Routing Protocol with Overload Control for Group Mobility in Delay-Tolerant Networking
## 4 Simulation Results
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Simulation time (s) & 43,200 \\ Number of simulation iteration & 50 \\ Transmission range (m) & 10 \\ Transmission speed (Mbps) & 2 \\ Mobility model & Group random waypoint \\ Node movement distance (m) & 400 \\ Group speed (m/s) & 1.0 \\ Number of nodes per group & 10 \\ Number of groups & 10 \\ Group range & 100 \\ Buffer size (Mbytes) & 10–100 (default: 50) \\ Message time-to-live (m) & 60–600 (default: 300) \\ Message size (Mbytes) & U[0.1,0.6]–U1.0.1,5] (default: U[0.5,1.0]) \\ Message generation interval (s) & U[25,35] \\ \(T_{p}\) & 0 \\ \(T_{r}\) & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parameter values. Figure 5 shows the delivery ratio for varying buffer size. Delivery ratios of all the considered protocols increased as buffer size increased but it saturated as the buffer size increased to accommodate messages sufficiently. Routing protocols with overload control had a significantly higher delivery ratio, since they efficiently reduced unnecessary message forwarding. The proposed protocol using group delivery predictability and proactive overload control had a higher delivery ratio by proactively reducing messages that were delivered to a node within the same group as the destination nodes of the messages. Figure 6 shows the overhead ratio for varying buffer size. Overhead ratios of all the considered protocols decreased as buffer size increased. This is because delivery ratio increases as buffer size increases due to the increase of the number of successfully delivered messages, as shown in Equation (9). As can be expected, routing protocols with overload control had significantly lower overhead ratio, since they efficiently reduced unnecessary message forwarding by overload control. The proposed protocol using group delivery predictability and proactive overload control had a lower overhead ratio by proactively reducing messages that were delivered to a node within the same group as the destination nodes of the messages. Figure 5: Delivery ratio for varying buffer size. Figure 6: Overhead ratio for varying buffer size. Figure 7 shows the delivery latency for varying buffer size. Delivery latencies of all the considered protocols increased as buffer size increased, since a large buffer accommodates more messages, and thus more time is needed to deliver a message to a destination node through transmission with limited bandwidth and limited contact time. Since protocols with overload control had smaller copies of messages for a given buffer size, more time was needed for them to be delivered to the destination node using a smaller number of forwarded messages. The proposed protocol had the largest delivery latency due to proactive overload control. Figure 8 shows the delivery ratio for varying the message size with a buffer size of 50 Mbytes. The delivery ratios of all the considered protocols decreased as message size increased. This is because higher messages size generates more message drop due to buffer overflow, and thus results in a lower delivery ratio. The protocols with overload control had a significantly higher delivery ratio than those without overload control by efficiently reducing unnecessary message forwarding. The proposed protocol using group delivery predictability and proactive overload control had a higher delivery ratio by proactively controlling overload. Figure 8: Delivery ratio for varying message size. Figure 7: Delivery latency for varying buffer size. Figure 9 shows the overhead ratio for varying message size with a buffer size of 50 Mbytes. Overhead ratios of all the considered messages increased as message size increased due to the decreased number of successfully delivered messages. Routing protocols with overload control had a significantly lower overhead ratio. The proposed protocol using group delivery predictability and proactive overload control had a lower overhead ratio because of proactive overload control.