— This paper mathematically frames the relation between window-based and rate-based congestion control algorithms, when the assumption of variable round-trip time conditions is introduced. Under this hypothesis, the local stability analysis of a specific class of source, window-based controls is first developed; then a new, rate-based control suitable for use by multimedia streams is proposed. The novel strategy is demonstrated to guarantee consistent and intra-fair throughput allocation, good responsiveness and satisfying smoothness, even in a first, easy-to-implement version.