Adaptive rate control for streaming flows over the Internet

The existing end-to-end TCP congestion control algorithm is well suited for applications that are not sensitive to delay jitter and abrupt changes of the transmission rate, such as FTP data transfer, but it is not recommended for delivering video data, whose perceived quality is sensitive to delay jitter and changes in the sending rate. In particular, the window-based control of Reno TCP congestion control causes burstiness in data transmission, which not only requires large buffers at the client side to provide a smooth playout but also may provoke bursts of lost packets difficult to recover via forward error correction techniques. This paper proposes an adaptive rate-based control (ARC) algorithm that striclty mimics the real-time dynamics of TCP and is based on an end-to-end mechanism to estimate the connection available bandwidth. Computer simulations using ns-2 have been developed to compare the ARC with the Reno TCP and with the TCP-Friendly Rate Control (TFRC) algorithm. Single- and multibottleneck scenarios in the presence of homogeneous and heterogeneous traffic sources have been considered. Simulations have shown that the ARC algorithm improves fairness and is friendly toward Reno. On the other hand, TFRC revealed itself not to be friendly toward Reno since it mimics only the long term behaviour of Reno TCP. Finally, simulations have shown that ARC remarkably improves the goodput with respect to TFRC and Reno in the presence of lossy links.