The analysis of QoE and QoS of adaptive real-time applications provides a challenging task in the current Internet. Here, we study major characteristics of Skype user satisfaction. For this purpose we estimate the loss and delivery time variation by inter-arrival times (IAT) between packets and packet lengths (PL) of an individual unidirectional flow. Extremes of the IAT and PLs impact on the QoS profile. We propose the estimates of the mean delivery time variation of complete packets per cluster, that influences the mean delay variation, the overall and mean byte losses, the required channel capacity to provide a desirable loss rate and the corresponding quantiles of a lossless period.