# Enhancing Cache Robustness in Information-Centric Networks: Per-Face Popularity Approaches
## 5 Results
### Varying Number of Attackers  
To further understand how these three algorithms work under different conditions, we turn our attention to varying the number of attackers (or, more correctly, the number of faces under attack that are dominated by the attackers). In the scenarios used for these tests, the cache size is 100 (1%), the attackers' request frequency is 720 requests/second, and the regular consumers request 120 requests/second. Arguably, it is reasonably difficult for attackers to overwhelm many faces on a content storage router, but we wanted to test out the algorithms' performance under stressful conditions. If any attack variation has a significant impact on PFP-DA, it will affect a larger percentage of attackers. PFP-DA would not benefit from normalizing contributions directly, as it did with the single attacker in varying frequency scenarios. The data in Table 9 for the Simple Topology give us insight into the typical performance of algorithms, including when there are no attacks occurring. The zero-attacker scenario gives a baseline for each of the caching algorithms under consideration. For ST, since there are ten total consumers, one attacker is 10%, three attackers are 30%, and so on. We tested variations from zero attackers all the way up to seven attackers, which are 70%. In Figure 6, the pollution percentages for LFU-DA and LRU remain very similar, with PFP-DA outperforming both from about the 10% up to the seven-attacker (70%) scenarios. At around the higher percentage of attackers, the gap closes substantially as PFP-DA is overcome with cache pollution. Important to note, however, is that the quality of content remaining in the cache is not captured with the overall cache pollution percentage data. The hit rates give us a much better picture of this in Figures 7 and 8. Both the overall and top 50 item hit rates take on very similar shapes, graphically. LRU, largely by coincidence, overtakes LFU-DA around the 50% attacker mark. This is largely because LFU-DA is based on request frequency, while LRU is not. Therefore, LRU depends entirely on recency and is affected only due to attacker content being more recently accessed as the number of attackers increases. Thus, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Algorithm** & **\# Attackers** & **\% Attackers** & **Pollution \%** & **Hit \%** & **Top 100** & **Top 50** \\ \hline PFP-DA & 0 & 0.00\% & 0.00\% & 20.69\% & 69.67\% & 82.96\% \\ LFU-DA & 0 & 0.00\% & 0.00\% & 14.82\% & 47.55\% & 55.59\% \\ LRU & 0 & 0.00\% & 0.00\% & 12.17\% & 38.59\% & 46.40\% \\ PFP-DA & 1 & 10.00\% & 15.00\% & 19.02\% & 62.80\% & 75.53\% \\ LFU-DA & 1 & 10.00\% & 36.00\% & 12.67\% & 41.17\% & 50.00\% \\ LRU & 1 & 10.00\% & 36.00\% & 8.82\% & 28.72\% & 34.64\% \\ PFP-DA & 3 & 30.00\% & 41.00\% & 16.29\% & 54.60\% & 66.76\% \\ LFU-DA & 3 & 30.00\% & 65.00\% & 9.16\% & 29.78\% & 35.31\% \\ LRU & 3 & 30.00\% & 64.00\% & 5.86\% & 19.34\% & 23.50\% \\ PFP-DA & 5 & 50.00\% & 68.00\% & 12.67\% & 43.89\% & 53.83\% \\ LFU-DA & 5 & 50.00\% & 74.00\% & 3.17\% & 9.62\% & 9.77\% \\ LRU & 5 & 50.00\% & 74.00\% & 3.86\% & 12.95\% & 15.82\% \\ PFP-DA & 7 & 70.00\% & 83.00\% & 7.97\% & 27.88\% & 34.80\% \\ LFU-DA & 7 & 70.00\% & 85.00\% & 0.70\% & 1.83\% & 1.67\% \\ LRU & 7 & 70.00\% & 88.00\% & 2.07\% & 6.91\% & 8.57\% \\ \hline \hline \end{tabular}
\end{table} 
Table 9: ST with size 100 cache, 720 attack frequency, and varying number of attackers. the LRU data are arguably affected indirectly, whereas LFU-DA and PFP-DA are primarily affected by frequency, which means they are directly affected by incoming frequencies. The difference between PFP-DA and both LRU and LFU-DA is remarkable. Even as the number of attackers increases, and PFP-DA is affected, it still performs substantially better than LRU and LFU-DA. We note that PFP-DA has a better hit rate (overall) by 5-9% during the increase in attacks. Even more interesting is that PFP-DA still maintains an almost 35% hit rate for the top 50 items, even as LFU-DA is entirely overwhelmed.