Evaluation of IPsec overhead for VoIP using a bare PC

In a bare PC softphone, the VoIP application runs directly on the hardware without any Operating System (OS). Such softphones are useful when security and/or performance concerns outweigh the need for a conventional system. We evaluate the overhead of IPsec for VoIP in a small test LAN using a bare PC softphone The results show that 1) for incoming packets, the difference between the processing time in tunnel and transport modes is about 0.02 ms regardless of voice packet size; 2) the processing overhead increase percentage for incoming packets compared to outgoing packets is largest for ESP without authentication in tunnel mode, and smallest for ESP with either authentication option in transport mode; 3) if UDP processing is eliminated, a throughput increase between 6-14% may be achieved for incoming packets; 4) the throughput increase on a bare PC softphone relative to an OS-based softphone is between 8-15%, and the difference due to varying the voice packet size (except for 40 ms packets) is less than 3%; 5) intrinsic jitter on a bare PC softphone is negligible, and maximum delta (packet inter-arrival time) on a compatible Linux softphone is twice that on a bare PC softphone.