The traffic characterization of adaptive real-time applications provides a challenging engineering task of the current Internet. Here the arrival and packet length processes arising from a unidirectional VoIP flow of Skype packets are investigated by statistical means. The mean traffic load offered by the packet flow to a virtual link of limited capacity in a finite observation period is calculated and the mean and upper bounds for the time without loss are derived. A possible characterization of the packet arrival process by a properly chosen non-linear GARCH (1, 1) model is presented.