Performance evaluation of software virtual private networks (VPN)

Virtual private networks implemented in software provide an economic and accessible alternative to hardware VPN solutions. Software VPNs may have a significant impact on performance, producing high CPU usage and limiting network throughput. This paper presents the performance measurements of several VPN programs. The results over a 100 Mb/s Ethernet link show that the transference speed can degrade in more than 65% while the CPU usage can reach 97%, when strong encryption is enabled. Compression implemented at the user level adds an additional CPU overhead that has a negative effect on the performance. The results over a low speed serial link show that the CPU usage is not significantly affected by the VPN. Furthermore, compression can be enabled without overhead, increasing the network throughput when the data is compressible