Characteristics of QoS parameters for VoIP in the short-haul Internet

We describe a number of quality of service (QoS) parameters for real-time voice applications and measure some factors, such as bidirectional packet delay, jitter, loss and out-of-ordered arrival behavior, influencing voice quality even in the short haul Internet. Our measurement results show that: (1) bidirectional delay is usually unimodal for 6 minute samples and the distribution is close to lognormal distribution when the traffic load becomes heavier; (2) jitter, i.e. delay variance, distribution is slightly asymmetric compared to the hypothesis of normal distribution and has higher probability on the right hand side; (3) consecutive loss of voice packets occurs irrespective of the diversity of packet size and packet departure interval and the degree of the consecutive loss is more significant when the packet size becomes bigger; (4) the most congested time slot is 7 pm to 11 pm. Moreover, the results address that toll-level voice quality can be achieved in the short haul Internet when the echo canceller is properly deployed at each end system and consecutive packet losses are also constrained in the intermediate nodes