The performance of two-dimensional media scaling for Internet videoconferencing

Until mechanisms for true real-time network communications are deployed and pervasive, one must rely on adaptive, best-effort congestion control methods to provide acceptable levels of service for interactive, real-time multimedia applications. Here we report on our experiences with a novel media-scaling congestion control scheme that was implemented in an experimental version of the Intel ProShare videoconferencing system and tested over the Internet. The media scaling scheme is unique in that it employs two-dimensional media scaling-the bit-rate and packet-rate of media streams are independently scaled. The goals of our study were (1) to empirically assess the performance improvement of two-dimensional media scaling over the simpler, and more commonly employed, one-dimensional scaling approaches and (2) to determine if it was possible to sustain ProShare conferences for a significant enough fraction of the time that two-dimensional scaling could be considered effective. We observed that systems using one-dimensional and two-dimensional scaling were both able to sustain conferences and that the two-dimensional scaling system always produced conferences with greater effective throughput. Our study provides empirical evidence that two-dimensional media scaling can be used effectively to ameliorate the effects of congestion in the Internet and can significantly extend the usability of an interactive multimedia application on the Internet