# DYNASTI--Dynamic Multiple RPL Instances for Multiple IoT Applications in Smart City
## 5 Performance Evaluation and Results
### Results
#### 5.5.1 Varying the Number of Nodes  
The impact between the DYNASTI solution and _Static Instances_ is evaluated in the scenarios through network parameters when varying the number of nodes in the network, since the number of nodes will directly influence the number of sent control messages, end-to-end delay, energy consumption, and lost packets. We employed the 13, 25, and 37 as different scenarios of number of nodes (including the sink node, which is not evaluated). The node configurations were defined in Section 5.1, while the number of scheduling, instances, applications, and the random generation of scheduling are defined in Section 5.4. Figure 4, described in the previous section, provides an example of how the DYNASTI solution works on the scenarios; it explains how the scheduling of instances works. DYNASTI and _Static Instances_ have the same configurations, with two exceptions. First, _Static Instances_ does not have sporadic applications. Second, in _Static Instances_, all applications send control and application messages throughout the total simulation time. Table 3 presents the scheduling of the DYNASTI solution. Only Application 1 is active in Scheduling 1; therefore, it uses the entire network resource to transmit data. The _Message Interval_ column specifies the application message interval in minutes--for instance, one message per node every five minutes. Unlike Scheduling 1, Scheduling 2 works differently: when Application 2 arises sporadically, the scheduler changes the instance of the Application 1 to adapt your traffic class and free up more resources. Hence, the message interval of Application 1 in Scheduling 2 (Instance 30) in the DYNASTI approach is one message for each 15 min. The time duration of Scheduling 2 is the same of Application 2 (i.e., 20 min) and, after its execution has ended, Instance 10 is reactivated. It is worth noting that the DYNASTI solution interrupts control and application messages when the sporadic application is not within 20 min of execution. When comparing different number of nodes, Figure 7(a) shows that DYNASTI results in a much lower number of control messages for 25 (38.09%) and 37 (43.75%) scenarios than _Static Instances_. For instance, the number of control messages with 25 nodes in _Static Instances_ is similar to the number of control messages with 37 nodes in DYNASTI. Figure 7(b) shows that the lowest end-to-end delay is achieved when DYNASTI is used; the difference between the two approaches increased as the number of nodes increased. This greater reduction in the number of control and application messages, as well as the decreased delay with the DYNASTI solution can be explained by the efficiency of more flexible and dynamic management of multiple instances and applications, making it possible to interrupt instance control and application messages. This efficiency tends to improve with increasing node numbers for DYNASTI as more nodes result in more control and application messages as well as delay. Therefore, DYNASTI enables more scalability with respect to the number of network nodes. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Application** & **Instance** & \begin{tabular}{c} **Traffic** \\ **Pattern** \\ \end{tabular} & \begin{tabular}{c} **Traffic** \\ **Type** \\ \end{tabular} & \
\begin{tabular}{c} **Messages** \\ **Interval** \\ \end{tabular} &
\begin{tabular}{c} **Scheduling** \\ \end{tabular} \\ \hline
1 & 10 & Regular & Normal & 5 min & 1 \\
1 & 30 & Regular & Normal & 15 min & 2 \\
2 & 20 & Sporadic & Critical & 3 min & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Scheduling for DYNASTI in scenarios varying the number of nodes. Figure 9(a) compares the amount of lost application messages between the DYNASTI and _Static Instances_. The DYNASTI solution for all scenarios lost fewer messages than _Static Instances_; the difference was the highest in the 25 and 37 nodes' scenarios, _Static Instances_ has two times more losses than DYNASTI for these two scenarios.