# Performance Evaluation of Mobile RPL-Based IoT Networks under Hello Flood Attack
## 6 Performances Analysis
### The Column Mobility Model (CMM)  
#### 6.1.1 Packet Delivery Ratio  
Figure 2 provides a comprehensive view of PDR dynamics in a mobile environment using the CMM mobility model, both with and without the Hello Flood attack. The \(x\)-axis delineates the number of nodes, ranging from 10 to 60, while the \(y\)-axis represents the PDR percentage, spanning from 0% to 100%. The graph is segmented into eight sets of bars, each denoting different percentages (10%, 20%, 30%, 40%) of malicious nodes. These sets are further categorized into two conditions: the mobile environment without the Hello Flood attack and the mobile environment with the attack, with each condition  
color-coded for clarity and accompanied by corresponding legends. Upon analysis, several trends emerge: Firstly, as the number of nodes increases, there is a noticeable decrease in the PDR across all scenarios, particularly pronounced when nodes are under attack. Secondly, when there are no malicious nodes present, the PDR remains relatively high, indicating efficient packet delivery. However, as the percentage of malicious nodes escalates, the PDR steadily declines, highlighting the adverse impact of attack nodes on overall delivery performance. Lastly, the presence of attack nodes, especially at higher percentages, significantly exacerbates the decline in the PDR, underscoring the detrimental effects of the Hello Flood attack on network reliability.  
The CMM imposes constraints on node movement, primarily directing nodes to navigate around a central column. This restricted mobility pattern creates congestion in certain network areas, facilitating opportunities for malicious nodes to disrupt communication and interfere with packet delivery. Moreover, in the CMM, nodes synchronize their movement with the central column, rendering the network susceptible to coordinated attacks such as the studied attack, the Hello Flood attack, where multiple malicious nodes flood the network with excessive traffic. This synchronized movement amplifies the impact of such attacks, resulting in increased packet loss and a decline in the Packet Delivery Ratio (PDR). Additionally, malicious nodes can exploit the CMM's boundary handling mechanism, which reverses direction upon reaching simulation area boundaries, to further disrupt communication and interfere with packet delivery. For instance, strategically positioned malicious nodes near the simulation area's edges can intercept and manipulate packets, exacerbating the decrease in the PDR. Furthermore, the structured movement pattern of the CMM, with nodes collectively advancing towards specific targets, heightens the network's vulnerability to targeted attacks like the Hello Flood attack. Malicious nodes can strategically position themselves along the column's path or near the target destination, launching coordinated attacks that significantly decrease the PDR. Overall, CMM networks are very likely to be interrupted because of their limited mobility patterns, synchronized movement, boundary handling mechanisms, and vulnerability to targeted attacks.