Improving the Start-up Performance of the TFRC Protocol

The transmission control protocol (TCP) Friendly Rate Control (TFRC) protocol emulates a TCP-like slow start algorithm, which is known to cause two problems: (1) takes many round-trip times to reach the optimal operating point; (2) misleads the sender to send too many packets too quickly at the end of the slow start phase. In this paper, we propose a modified measurement-based slow start mechanism, called bandwidth estimate start (BE-start), to improve the start-up performance of the TFRC protocol. The BE-start employs an effective online bandwidth measurement technique to update the sending rate with appropriate value dynamically. By adapting to network conditions during the start-up phase, the sender is able to increase the sending rate quickly without incurring a risk of buffer overflow and multiple losses. Simulation experiments show that the BE-start can significantly improve the TFRC protocol performance under various bandwidths, buffer sizes and round-trip times. The method avoids both under-utilization due to premature slow start termination, as well as multiple losses due to increasing the sending rate too fast.