Abstract. TFRC (TCP Friendly Rate Control) is a rate-based congestion control protocol for non-TCP flows. TFRC controls the sending rate by using the TCP throughput equation considering the triple duplicate ACKs and the timeouts. However, this equation provides the conservative throughput bound of TCP. This conservativeness causes lower throughput and slower response time for TFRC than those for TCP. In this paper, we propose the Adaptive TCP Friendly Rate Control (ATFRC) protocol. Reflecting the transient behavior of TCP, we divide the throughput calculation periods into two. For each period, we adapt the sending rate based on different TCP throughput bounds. Simulation results show that the proposed algorithm gets closer to the long-term fair share of TCP than that of TFRC. In addition, ATFRC has faster convergence time than TFRC when bandwidth is available.