Application Level Performamce of Multimedia Services

Quality of Service (QoS) is a difficult term to define for multimedia applications. The main reason is that both audio and video quality are subjective and difficult to quantify. Much work has been done in the past to map the subjective quality of video and audio into measurable quantities. Unfortunately, when it comes to IP environments, not much experience and mathematical work exists that can be used to define robust metrics for measurement of QoS. In this paper, we report on measurements of multimedia QoS and try to map subjective criteria to discrete measurables in terms of packet loss rates, packet delays, and other quantities. We report the results of measurements done at the application level and show how network characteristics affect the perceived quality of multimedia applications. In particular, we analyze the application traffic generated by MBone clients in a distributed network education scenario. In order to measure the traffic, we have implemented software on a non-intrusive probe developed by NIKSUN INC.\footnote{http://www.niksun.com} that can accurately monitor all traffic from a variety of networks. We have developed MBone aware software modules which can not only play back the recorded streams but also provide the essential statistics in real-time. We report in detail the results of our study of a particular end-to-end MBone session