| In this paper, we present adaptation strategies for real-time video streams over Stream Control Transmission Protocol (SCTP), where we switch among several versions of the coded video to match the available network bandwidth accurately, and meet client delay constraints. By monitoring the application buffer at the server, we estimate the current and future server buffer drain delay, and derive the transmission rate to minimize client buffer starvation. We also show that the adaptation accuracy can be significantly improved by a simple scaling to SCTP send-buffer size. The proposed mechanisms were evaluated through simulation and real Internet traces. Performance results show that the adaptation mechanism is responsive to bandwidth fluctuations, while ensuring that the client buffer does not underflow, and that the quality adaptation is smooth so that the impact on the perceptual quality at the client is minimal. |