SIP over IP VPN: Performance Analysis

With rapid growth in use of multimedia applications, including IP Telephony (also known as Voice over IP), the demand for security and privacy of communications has significantly increased. Given the fact that IP Telephony utilizes public IP infrastructure, deployment of IP VPN is one approach to protect traffic of interest. However, VPN is presumed to have a negative impact on VOIP performance due to additional packet overheads, authentication, integrity check, encryption, and extra CPU processing involved in the process. In this paper we simulate behavior of a SIP-based VOIP connection running over an IP VPN tunnel. OPNET IT GURU is used as the simulation tool. Few studies examined role of Quality of Service (QoS) parameters such as call signaling and employed VPN protocols, but the role of parameters’ arising from network environment, including design issues, were neglected. Bearing this in mind, this research considers several possible scenarios. It compares performance of VOIP calls based on end-to-end delay, delay variation and call setup time for different network configuration (with and without VPN). VPN itself didn’t show any negative impact on end-to-end delay. However, combination of network design and VPN show an impact on end-to-end delay.