Analysis of IPSec overheads for VPN servers

Internet protocol security (IPSec) is a widely deployed mechanism for implementing virtual private networks (VPNs). This paper evaluates the performance overheads associated with IPSec. We use Openswan, an open source implementation of IPSec, and measure the running times of individual security operations and also the speedup gained by replacing various IPSec components with no-ops. The main findings of this study include: VPN connection establishment and maintenance overheads for short sessions could be significantly higher than those incurred while transferring data, and cryptographic operations contribute 32 - 60% of the total IPSec overheads.