# Efficient Data Delivery Scheme for Large-Scale Microservices in Distributed Cloud Environment
## 4 Simulation Scenarios and Results
### Assessment of Scaling Number of Brokers  
This subsection evaluated the scalability metric of our proposal in comparison to other similar schemes. In this scenario, the number of brokers was increased from 200 to 500 in steps of 100 for each of the four simulations conducted with each scheme. The capabilities of the comparable pub/sub systems were investigated to support many-to-many communication patterns among the brokers' microservice clients. Each broker was specifically in \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Modal Algorithms** & **ECBC\_Proposal** & **PubSubCoord-like** & **PSECTO** \\ \hline \(p=5\); \(n=25\) & 9.08 & 10.87 & 8.48 \\ \(p=5\); \(n=50\) & 8.88 & 10.81 & 8.40 \\ \(p=1\); \(n=5\) & 7.98 & 10.78 & 8.34 \\ \(p=1\); \(n=10\) & 6.52 & 10.48 & 8.33 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: AFT (%) in the multi-modal model scenario. Figure 7: ADL in the multi-modal model scenario. charge of 100 event channels, of which microservice clients published or subscribed to 70% on the local level and selected the remaining 30% from the outside brokers. Accordingly, multi-producer and multi-consumer scenarios of event channels were generated in the experiments to measure the ADL, AFT, and ND results of data delivery with the compared schemes. The results are shown in Table 3 and Figures 8 and 9. As shown in Table 3, our proposal achieved the best outcome in terms of AFT. A small increase in average traffic exchanged among brokers in the system, from 8.07% to 8.50%, was observed when the number of brokers was increased from 200 to 500, respectively. The PubSubCoord-like scheme experienced the highest (worst) percentages of average exchanged traffic, because the edge brokers in this approach have to send data through relay cloud brokers for joint event channels among them. Figure 8 plots the ADL results of the three approaches measured from the performed experiments. Our proposal has a much lower ADL than that of the PubSubCoord-like scheme. For example, in the simulated example with 500 brokers the ADL value out the proposed scheme was 49.1 ms, while that of PubSubCoord-like was 73.41 ms. On average, the ADL of the proposed method was approximately 65% that of PubSubCoord-like. On the other hand, the PSECTO scheme achieved the best (lowest) ADL values in all of the tested cases. The PSECTO technique uses numerous direct connections between edge brokers to convey data for joint event channels among these brokers, which accounts for this remarkable result. Nevertheless, scaling issues may arise due to the high resources required by the pub/sub brokers for keeping the topic overlay networks operational in this approach. Therefore, the average ND values in the experiments were calculated in order to scrutinize the issue further. Figure 9 shows the brokers' average node degrees in the three schemes. The PSECTO scheme experienced the highest average ND values in all the test cases of the evaluation setting, as this approach promotes direct connections between brokers that have joint event channels for data delivery. Specifically, the average broker  
Figure 8: Effect of scaling the number of brokers on average delays. \begin{table}
\begin{tabular}{c c c c} \hline \hline \# Brokers**Algorithms** & **ECBC\_Proposal** & **PubSubCoord-like** & **PSECTO** \\ \hline
200 & 8.07 & 9.44 & 8.60 \\
300 & 8.28 & 9.53 & 8.75 \\
400 & 8.39 & 9.59 & 8.88 \\
500 & 8.50 & 9.61 & 8.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: AFT (%) with scaling number of brokers. node level increased significantly from 147 to 223 as the number of brokers increased from 200 to 500, respectively. Note that the higher average number of connections maintained by each broker to other brokers means that more of the broker's resources are consumed to maintain the connection states. While the proposal achieved much lower average node degree results than the PSECTO model, the PubSubCoord-like scheme achieved the best ND results in all the cases tested.