# Feasibility Assessment of a Fine-Grained Access Control Model on Resource Constrained Sensors
## 5 Performance Evaluation
### Performance Analysis
#### 5.2.1 Response Time  
The resulting response time measurements after the launch of the seven feasible series with one and two hops are shown in Table 10. Such mean response times increase slightly with the length of the policy instances, as expected, ranging from 216 ms (\(IS_{1}\) and APBR) to 232 ms (\(IS_{3}\) and CBOR). To compare, Figure 7 shows the average response time with one hop, and regardless of sporadic picks, most response times remain in a constant, low range. This value is very good considering that the maximum acceptable delay in interactive E2E data transactions specified by [PERSON] [40] is 1000 ms.  
In all cases, Figure 7 also indicates that the maximum response time in the worst sporadic case is below 720 ms and under the accepted quality standards for interactive applications.  
The impact of Hidra depending on the network topology is analyzed under two network configurations: one and two hops. Figure 8 shows a composition of the measurements with the two configurations when a security association is established and the policy instance is \(IS_{1}\). The accurately measured values of Table 10 indicate that a second hop results in a proportional increase of 240 ms on average. This value could also be considered as a referential increment per hop for further estimations aiming at large-scale deployments.  
\begin{table}
\begin{tabular}{l l c c c c c c} \hline \hline \multirow{2}{*}{**IS**} & \multirow{2}{*}{**Format**} & **Network** & **Length** & **Average** & **Median** & **Standard** & **95\% Configuration** \\  & & **(Hops)** & **(Byte)** & **(ms)** & **(ms)** & **Deviation (ms)** & **Int. (ms)** \\ \hline \(IS_{1}\) & APBR & 1 & 2 & 215.39 & 213.09 & 28.79 & (209.08,221.70) \\ \(IS_{1}\) & APBR & 2 & 2 & 357.56 & 343.97 & 183.44 & (317.37,397.76) \\ \hline \(IS_{2}\) & APBR & 1 & 7 & 219.92 & 213.60 & 37.15 & (211.78,228.06) \\ \(IS_{3}\) & APBR & 1 & 9 & 221.80 & 213.55 & 62.54 & (208.10,235.51) \\ \(IS_{4}\) & APBR & 1 & 32 & 222.48 & 213.37 & 44.51 & (212.73,232.23) \\ \hline \(IS_{1}\) & CBOR & 1 & 14 & 221.98 & 215.28 & 20.35 & (217.51,226.44) \\ \(IS_{2}\) & CBOR & 1 & 81 & 226.73 & 219.49 & 43.54 & (217.19,236.28) \\ \(IS_{3}\) & CBOR & 1 & 123 & 231.51 & 223.73 & 34.63 & (223.92,239.10) \\ \hline \hline \end{tabular}
\end{table}
Table 10: Response time measures.  
Figure 7: Response time of security association establishment considering up to seven series of 80 requests.  
Beyond the absolute values, attempting to compare with similar existing measurements, one related comparable response time value has been found in the literature [41]. The measurements are performed by integrating C2 CDSs, and the analysis reveals that the response time for the authorization response starting when the subject sends the request is 480.96 ms (with one hop). The response time of Hidra is lower even with a worse network bit rate and, therefore, is better. In addition, in these comparison tests, there is no mention of additional performance indicators such as energy consumption.