Characterizing user-perceived impairment events using end-to-end measurements

Abstract

SUMMARYMeasures of quality of service (QoS) must correlate to end-user experience. For multimedia services, these metrics should focus on the phenomena that are observable by the end-user. Metrics such as delay and loss may have little direct meaning to the end-user because knowledge of specific coding and/or adaptive techniques is required to translate delay and loss to the user-perceived performance. Impairment events, as defined in this paper, are observable by the end-users independent of coding, adaptive playout or packet loss concealment techniques employed by their multimedia applications. Time between impairments and duration of impairments are metrics that are easily understandable by a network user. Methods to detect these impairment events using end-to-end measurements are developed here. In addition, techniques to identify Layer 2 route changes and congestion events using end-to-end measurements are also developed. These are useful in determining what caused the impairments. End-to-end measurements were conducted for about 26 days on 9 different node pairs to evaluate the developed techniques. Impairments occurred at a high rate on the two paths on which congestion events were detected. On these two paths, congestion occurred for 6-8 hours during the day on weekdays. Impairments caused by route changes were rare but lasted for several minutes.

An algorithm for fitting MMPP to IP traffic traces

“…It was shown that the method from [1] results in a reasonably accurate MMPP model for medium sized traces. However, this method may not be very accurate when there is a need to model longer traces that exhibit diurnal traffic variations [4]. In this paper we modify the method proposed in [1] and show, using several 24 hour traces, that the new method provides a better model for longer traces at the expense of an increased number of states.…”