## 5 Evaluation
### Performance Benchmark
#### 5.3.2 Number of Parameters as a Variable  
Experiments in this category were carried out to see how a different number of parameters affects the overall performance of the implemented platform in both standalone and clustered versions. In Figure 10, for example, the SpO2, the pulse rate and the SOS information channels use one parameter each; the location information channel has two parameters, while the spirometry information channel has 13 parameters for each measurement. Four experiments were conducted in this category, but unlike the previous category, the publication rate is fixed at one publication per second in order not to load the application servers. The number of parameters is varied instead, ranging from one to 700 parameters. Each measurement in all experiments lasted five minutes, generating 300 data. Each measurement was performed three times to ensure data consistency, and the first 1% of the captured data is removed from every measurement to avoid the start-up effect of the application servers in serving incoming requests. All measurement data are averaged and plotted alongside their confidence intervals at the 95% confidence level, just like in the previous category. A comparison of total average publication and notification times between the secured and non-secured standalone IIP deployments is shown in Figure 19a. The time difference starts at about 85 ms when one parameter is used, and the gap increases almost linearly to around 125 ms when 700 parameters are used. This gap represents the implemented security mechanism's overhead in the standalone IIP set-up. Figure 19b depicts a comparison of publication and notification latency between the secured and non-secured clustered IIP set-ups. The time difference is stabled across all measurements at about 90 ms. From Figure 19a,b, it can be seen that the additional overhead of the security mechanism does not change  
much with the increased number of parameters being used for both standalone and clustered deployments of the IIP. A comparison of the average latency difference between secured standalone and clustered IIP deployments is shown in Figure 19c. When only one parameter is used, the clustered set-up outperforms its a standalone rival with around a 20 ms difference. However, the clustered deployment suffers more latency overhead compared to the standalone version with the increasing number of parameters being used. With 100 parameters used, the clustered deployment performs worse than its standalone counterpart by around 365 ms, and it is further worsened as the number of parameters being used is increased. Figure 19d shows a comparison of average publication and notification times between non-secured standalone and clustered IIP set-ups. Almost similar to Figure 19c, the clustered version in this experiment wins in terms of the latency difference compared to its standalone counterpart by about 20 ms when only one parameter is used, but it suffers when the number of parameters increases. When  
Figure 19: Publication and notification time comparisons with the number of parameters as the variable: (**a**) Standalone secure _vs_. insecure; (**b**) Clustered secure _vs_. insecure; (**c**) Secure standalone _vs_. Clustered; (**d**) Insecure standalone _vs_. clustered. 100 parameters are used, the clustered set-up falls short by around 360 ms in latency performance compared to the standalone deployment. From the four experiments in this category (_i.e._, the number of parameters as the variable), it can be concluded that the clustered set-up of the IIP performs better than the standalone set-up when the number of parameters being used is low. The latency increase rate is higher for the clustered version compared to the standalone deployment as the number of parameters being used grows. This can be seen as a direct impact of the synchronization process between data nodes in the data layer, since synchronizing large amounts of incoming new data takes much more time than writing directly to one data store.