ABSTRACT: One of the major problems experienced with LAN-based video conferencing systems is the degradation of conference latency and fidelity due to network congestion. In this paper, we present a comprehensive transmission control framework describing the relationship of latency and fidelity to properties of human perception and network congestion. We discuss how network factors such as physical link capacity and size of maximum transmission units may exacerbate the effects of congestion on the conference and how the impact of congestion can be ameliorated through judicious adaptation of the media streams' bit and message rates. Finally, we demonstrate the ability of an adaptive transmission control algorithm based upon the framework to produce low-latency, high-fidelity conferences over congested internetworks.