University of Mostar
The paper presents the way to provide the security to one of the recent development in computing, cloud computing. The main interest is to investigate the impact of using Virtual Private Network VPN together with firewall on cloud computing performance. Therefore, computer modeling and simulation of cloud computing with OPNET modular simulator has been conducted for the cases of cloud computing with and without VPN and firewall. To achieve clear idea on these impacts, the simulation considers different scenarios and different form application traffic applied. Simulation results showing throughput, delay, server's traffic sent and received have been collected and presented. The results clearly show that there is impact in throughput and delay through the use of VPN and firewall.