In this book, the performance of voice and video traffic are analysed by investigating the effect of implementing VPN over WLAN on the basis of different quality of service parameters. Initially, quality of service parameters like packet delay variation, mean opinion score (MOS), packet end to end delay are considered. Three scenarios namely 'without firewall', 'with firewall' and 'firewall with VPN' are used. Then, quality of service parameters like throughput, load, delay, data dropped, media access delay, traffic received and traffic sent are focussed.