# Studying the Impact of a UDP DoS Attack on the Parameters of VoIP Voice and Video Streams
## 5 Results  
### Results When Only Voice Traffic Is Exchanged  
#### 5.1.1 Results from Normal Mode of Operation  
Figure 2 represents the traffic that goes through the Asterisk during normal operation. All subscribers talk to each other. There are two voice streams (VM1 calling VM2 and VM3 calling VM4), each with a rate of 42 kB/s. As can be seen, the traffic is normal for processing voice streams. The result is from the Asterisk FreePBX dashboard.  
Figure 3 shows the traffic that enters/exits the Asterisk FreePBX network interface card (NIC). The result is from Capsa free 11. As can be seen, the traffic that goes through the Asterisk network interface is the same as in Figure 2, except that it is summed.  
Figure 1: Topology of the modeled network.  
Figure 4 represents the traffic that is generated/processed by the VM3. The same traffic is generated/processed by the other VMs. As can be seen, if the traffic from the two virtual machines (VM3 and VM4) is summed, the traffic generated by the two voice streams that is processed by the Asterisk FreePBX is obtained.  
Figure 4: Traffic that proceeded/was generated from VM3 during voice calls.  
Figure 3: Asterisk NIC’s load during normal operation—voice calls.  
Figure 2: Traffic let through by Asterisk during normal operation—voice calls.  
Figure 5 represents what the CPU utilization of the Asterisk is for different time intervals. As can be seen from the graph, the CPU utilization is below 50%. There is only a single overshoot above 50%. In the general case, the load during the calls is around 20%.  
Figure 6 represents what the memory load of Asterisk was for the entire study period. As can be seen from the graph, the memory load is around 14%.  
Figure 7 shows the summarized information about the parameters of the voice stream that is exchanged between VM1 (192.168.2.3) and VM2 (192.168.2.6) in both directions--from VM1 to the Asterisk (192.168.2.2) Figure 7a, then from the Asterisk to the VM2 and vice versa. As can be seen from the figures, the values of the most important parameters--mean jitter and packet loss are within the norm.  
Figure 5: Asterisk’s CPU load during normal operation—voice calls.  
Figure 6: Asterisk’s memory load during normal operation—voice calls.  
Figure 8 represents how the jitter changes during the entire conversation in the direction from VM1 to the Asterisk and vice versa. As can be seen from the graph, there are only a few momentary spikes; otherwise, the jitter values vary between 0.5 and 1.5 ms.  
Figure 9 represents how the jitter changes during the entire conversation in the direction from VM2 to the Asterisk and vice versa. As can be seen from the graph, the result is similar to the result in Figure 8.  
Figure 8: Jitter variation for the voice stream between VM1 and the Asterisk—normal operation.  
Figure 7: Parameters of the voice stream between VM_1 and the Asterisk (**a**) and between VM_2 and the Asterisk (**b**) during normal operation.  
These results will be used as a reference. These results will be compared to the results obtained when Asterisk is attacked with a UDP DoS attack during audio conversations/calls between the users.