# PrECast: An Efficient Crypto-Free Solution for Broadcast-Based Attacks in IPv4 Networks
## 6 Performance Analysis of PrECast
### Simulation  
In this subsection, we present the message complexity and convergence analysis through simulation. We wrote a discrete event simulator using C. We implemented the traditional ARP protocol and PrECast for comparison. We set the ARP arrival rate to be two packets per minute for all hosts in the network. We considered a topology of having five access layer switches connected with a distribution layer switch. There are 20 hosts connected with every access layer switch. Our simulation topology is given in Figure 5. We ran the experiment for 60 min and collected the statistics on message complexity. We repeated the experiment 100 times and took the average to remove any simulation artefacts.  
In our simulation, we considered the ARP protocol with two different types of ARP-cache clearance processes. In the first type, all entries in the ARP cache table are cleared after the time-out. In this case, if the host needs the MAC address of a recently-used host, it needs to initiate the ARP resolution again. The second ARP-cache clearance scheme only clears the ARP-table entries that were not used until the time-out period. All recently-used entries are kept intact. For more detail on ARP-cache algorithms, please refer to [1]. The performance graphs are presented in Figures 6-9. It can clearly be seen that the PrECast protocol outperforms the conventional ARP protocol.  
In this section, we have analysed the theoretical performance of the PrECast architecture in terms of the message complexity and time to converge. We also simulated the PrECast protocol and compared its performance against the traditional ARP protocol. However, certain real-time performance parameters like CPU load on the switches and ARP-table lookup latency due to the PrECast protocol cannot be evaluated using simulation or theoretical results. Our future work involves implementing the PrECast protocol in real hardware and studying the performance parameters such as message complexity, time to converge, CPU load and ARP table lookup latency. We now summarize the implementation tasks and the main guidelines of the experimental test.  
Figure 5: Simulation topology.  
Figure 6: Traditional ARP process with no time-out.  
Figure 8: ARP process with time-out = 10, 20 and 30 min (Type 2).  
Figure 7: ARP process with time-out = 10, 20 and 30 min (Type 1).  
Figure 9: Number of ARP multicasts in PrECast.  
As the first task, we modify the kernel of a switch operating system, so that the switching process opens a Layer-2 frame and records the source IP address in order to create the MCAM table. The MCAM table is kept in the RAM of the switches. We then start an inter-switch communication process to create a multicast group. All PrECast-enabled switches join this multicast group. The pre-configured keys are installed by the network administrator in these switches for secure inter-switch communication. As per the state-transition diagram presented in Figures 3 and 4, PrECast switches handle ARP and DHCP queries. Then, we collect short-term and long-term statistics and compared with the results presented in this paper. We strongly believe that the results obtained from the experimental network, when available, will complete and corroborate the results presented in this paper. However, at the current stage, we leave the implementation as our future work.