## 6 Performance Evaluation
### Experiment 2: Jitter with Increasing Bitrate and Payload Size  
In this experiment, we varied the bitrate and payload size in the network and evaluated its impact on the jitter. Increasing the bitrate and payload size caused an increase in jitter, causing a significant impact on the network's performance. This can be seen in  
Figure 12: Bottleneck for Topology 3 (Child to Leader).  
Figure 13: Bottleneck for Topology 3 (Child to Child).  
Figures 14 and 15 in detail for Topology 1 and Topology 2, respectively. This experiment highlights the importance of carefully selecting the bitrate and selecting an appropriate payload size to avoid excessive jitter in the network. The jitter increases with the increase in bitrate as the number of datagrams being sent also increases, making the network congested. After a certain level of increase in the bitrate, the jitter starts to decrease. This decrease in jitter is due to high packet loss, as the number of datagrams exceeds the capacity of the network.  
As can be seen in Figure 14, overall in Topology 1, the optimal performance in terms of jitter is achieved with a packet size of 1000 bytes with a 100 kbps bitrate and 2.507 ms jitter. It could transfer the data with 0% packet loss as 100 kbps is before the bottleneck occurs. It can be observed from the results as shown in Figure 15 when the number of hops increases, there can be a significant increase in jitter. Both the topologies represent a similar trend, as the bitrate increases, the number of datagrams also increases, which leads to an increase in jitter. The optimal performance in Topology 2 is also achieved by a 1000-byte packet size with a 40 kbps bitrate. It could transfer data with 0% packet loss as the bitrate is not beyond the bottleneck scenario and 3.527 ms jitter.  
The detailed representation of the experiments performed for evaluation of the Thread network on varying the bitrate can be seen in Table 4. The results in Table 4 are generated from Topology 1 where a router node communicates with the leader node, for the default packet size of 1208 bytes in UDP transmission. It can be seen in the table that there are no packet losses till the provided bitrate reaches the bottleneck of 100 kbps. We can also see that with the increasing bitrate, the number of datagrams increases leading to congestion  
Figure 14: Topology 1: jitter with increasing bitrate and payload size.  
Figure 15: Topology 2: jitter with increasing bitrate and payload size.  
and ultimately packet losses. The same experiment is repeated for Topologies 2 and 3 to check the network performance in terms of jitter and packet loss with different packet sizes.  
The impact of varying bitrate and payload on jitter has also been observed on Topology 3, in both child-to-leader with network congestion and child-to-child communication scenarios. The network performance of these scenarios can be seen in Tables 5 and 6, respectively. It can be clearly seen that the jitter is much higher in the network congestion scenario of two hops communication, as compared to three hops communication. The \"0 ms\" jitter values in Table 5 indicate that no contact was made. This happens due to high bitrate, as the network becomes even more congested and communication becomes impossible.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Bitrate (kbps)** & \begin{tabular}{c} **Bitrate at** \\ **Receiver (kbps)** \\ \end{tabular} & \begin{tabular}{c} **Data Transferred** \\ **(KBytes)** \\ \end{tabular} & \begin{tabular}{c} **Data Received** \\ **(KBytes)** \\ \end{tabular} & \begin{tabular}{c} **Datagrams/s** \\ **(KBytes)** \\ \end{tabular} & \
\begin{tabular}{c} **Load/Total** \\ **Datagrams in** \\ **30 s (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Jitter (ms)** \\ \end{tabular} \\ \hline
5 & 5 & 18.9 & 18.9 & 0–1 & 0/16 (0\%) & 3.694 \\ \hline
10 & 10 & 37.8 & 37.8 & 1 & 0/32 (0\%) & 3.861 \\ \hline
20 & 20 & 74.3 & 74.3 & 2