A comparison of VoIP performance on IPv6 and IPv4 networks

We compare VoIP performance on IPv6 and IPv4 LANs in the presence of varying levels of background UDP traffic. A conventional softphone is used to make calls and a bare PC (operating systemless) softphone is used as a control to determine the impact of system overhead. The performance measures are maximum and mean delta (the time between the arrival of voice packets), maximum and mean jitter, packet loss, MOS (mean opinion score), and throughput. We also determine the relative frequency distribution for delta. It is found that mean values of delta for IPv4 and IPv6 are similar although maximum values are much higher than the mean and show more variability at higher levels of background traffic. The maximum jitter for IPv6 is slightly higher than for IPv4 but mean jitter values are approximately the same. On an overloaded 100 Mbps link, packet loss can reach close to 18% for IPv4 and 24% for IPv6, and the MOS degrades significantly. At moderate levels of background traffic, the IPv4/IPv6 throughput ratio is close to the ideal (theoretical) throughput ratio, but at high levels of background traffic, throughput for IPv6 declines slightly faster than for IPv4. In general, our results indicate that the difference in VoIP performance for IPv6 and IPv4 is negligible. Results for the bare PC softphone confirm that reducing system and application overhead lowers delta and jitter values regardless of the IP version.