End-to-end Voip Quality Measurement

The VoIP quality of service can be either estimated by analyzing the voice data flow characteristics, or by recording a transmitted voice probe over the whole VoIP transport chain and comparing it to the original. When the quality estimation by the voice data flow characteristics is deployed, the three most prominent degradation factors are observed – the packet loss, the packet delay and the delay variance (also called jitter). Depending on the estimation model, the values of these degradation factors are used to compute the resulting quality rating estimation. The end-to-end quality measurement provides more dependable results, however, it is also more technically and computationally demanding. We describe our experiences with both methods of quality evaluation and measurement. An experimental VPN for VoIP QoS measurements was created and a voice probe was sent through this network while end-to-end quality and degradation factors were observed. For end-to-end measurements we used our own developed equipment that allowed us to synchronize the original and recorded voice probe and obtain the timing characteristics. The obtained results are also discussed in this article.