# Rapid Restoration Techniques for Software-Defined Networks
## 5 Experimental Evaluation
### Performance Evaluation
#### 5.2.3 Path Installation Cost
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{8}{c}{**Path Length**} \\ \cline{3-11}  & & **20\%** & **30\%** & **40\%** & **50\%** & **60\%** & **70\%** & **80\%** & **90\%** & **100\%** \\ \hline \multirow{4}{*}{Algorithm 2} & NR & 44.4 & 61.5 & 70.5 & 76.1 & 78.2 & 80.7 & 83.8 & 84.8 & 86.8 \\  & Germany & 28.5 & 44.4 & 50 & 58.3 & 58.3 & 64.2 & 68.7 & 72.2 & 75 \\  & ERnet & 14.2 & 14.2 & 33.3 & 40 & 50 & 57.1 & 57.1 & 62.5 & 66.6 \\  & Brite1 & 16.6 & 16.6 & 37.5 & 50 & 58.3 & 57.1 & 57.1 & 62.5 & 72.2 \\  & Brite2 & - & - & - & 30 & 33.3 & 42.8 & 48.8 & 50 & 55.5 \\  & Brite3 & 28.5 & 28.5 & 37.5 & 50 & 58.3 & 64.2 & 57.1 & 62.5 & 61.1 \\ \hline \multirow{4}{*}{Algorithm 3} & NR & 33.3 & 38.4 & 41.1 & 42.8 & 43.4 & 46.1 & 48.3 & 48.4 & 47.3 \\  & Germany & 28.5 & 33.3 & 30 & 41.6 & 41.6 & 35.7 & 43.7 & 44.4 & 45 \\  & ERnet & 14.2 & 14.2 & 22.2 & 30 & 33.3 & 35.7 & 35.7 & 37.5 & 38.8 \\  & Brite1 & 16.6 & 16.6 & 25 & 30 & 41.6 & 35.7 & 35.7 & 43.7 & 38.8 \\  & Brite2 & 14.2 & - & 25 & 30 & 41.6 & 35.7 & 35.7 & 43.7 & 38.3 \\  & Brite3 & 14.2 & 14.2 & 25 & 30 & 41.6 & 35.7 & 35.7 & 43.7 & 44.4 \\ \hline \multirow{4}{*}{Algorithm 4} & NR & 44.4 & 61.5 & 70.5 & 76.1 & 78.2 & 80.7 & 83.8 & 84.8 & 86.8 \\  & Germany & 28.5 & 44.4 & 50 & 58.3 & 58.3 & 64.2 & 68.7 & 72.2 & 75 \\  & ERnet & 14.2 & 14.2 & 33.3 & 40 & 50 & 57.1 & 57.1 & 62.5 & 66.6 \\  & Brite1 & 16.6 & 16.6 & 37.5 & 40 & 58.3 & 57.1 & 57.1 & 68.7 & 72.2 \\  & Brite2 & 14.2 & - & 25 & 40 & 50 & 50 & 50 & 56.2 & 61.1 \\  & Brite3 & 28.5 & 28.5 & 25 & 50 & 50 & 50 & 50 & 56.2 & 61.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average cost reduction rate of Algorithms 1–3 are compared as a function of the normalized path length. Figure 10: The path set-up latency, that is, time required to install the network path, achieved by Algorithms 1–4 for the experimental topologies of Table 1 are illustrated as a function of the normalized path length. Figure 9: Process of measuring the cost of path installation. On the other hand, the performance of the proposed algorithms improved when the length of the paths increased. In terms of the set-up time, Table 5 presents the relative difference in the performance of Algorithms 2-4 in comparison to Algorithm 1. The relative difference is the percentage of increase or decrease in set-up time between the proposed approaches and Algorithm 1. The downwards arrow next to the percentage values of Table 5 indicates the decrease in set-up time while the upwards arrow indicates the increase. When the percentage path length was 20-30% the proposed algorithms mostly produced a slight increase in the time required to install alternative paths. In fact, the increase was less than 10% in most cases and 27% in the worst case. In contrast, the proposed approaches reduced the required time to install the alternative paths when the path length ranged from 40% to 100%. The reduction ratio was up to 70% for long paths and up to 40% for medium length ones. The reduction rate of Algorithms 2 and 3 was relatively better than that of Algorithm 4. This was due to the fact that in Algorithm 4, only half of the path's flow entries needed to be replaced. Finally, this latency measurement demonstrated the ability of the proposed approaches to reduce alternative paths' set-up times, particularly, for long and medium length paths. We have evaluated our path recovery algorithms under the headings: length, operation and latency. The proposed approaches do not come with the guarantee that the optimal shortest path will be found. However, experiments demonstrated that in general the increase in the path length cost was small compared to [PERSON]'s algorithm. A slight increase in the cost of path installation for short paths was observed, but for long and medium paths, the proposed approaches were more efficient, and achieved a good reduction in path installation cost.