Analysis And Application Of TFRC Congestion Control Mechanism

Nowadays most of applications in the Internet are based on TCP.TCP is a protocol with congestion control and avoidance schemes, which makes it stable and successful. However, with the growth of real-time multimedia application in the Internet, some non-TCP protocols without congestion control, such as UDP, are being widely used. These protocols lack of avoidance scheme, so that they would not decrease their sending rate while network congestion. Largely using them would rap the bandwidth of TCP flows. In order of healthy developing the real-time multimedia application, it's urgent to regulate the congestion behavior of the non-TCP flows. We need to develop a protocol, which can suit the multimedia application as well as be fair with TCP.In this way, some TCP-Friendly protocols and algorithms have been widely researched. In this paper, we would put emphasis upon one of the most successful TCP-Friendly protocols-TFRC (TCP-Friendly Rate Control) protocol.We first analyzed the TFRC's mechanism, we found out that the performance of Slow-Start of TFRC is not enough good. Its access performance is not good as TCP's. It leads to TFRC cannot achieve convergence quickly. In addition, TFRC would not retreat from Slow-Start by itself. Loss is the only exit signal. It may lead to large numbers of losses when the sending rate exponentially exceeds the bandwidth capability. We present a feedback congestion control scheme based on real-time transport protocol (RTP) and real-time transport control protocol (RTCP), which can satisfy the real-time delivery system with loss and delay requirements. The paper discusses a rate-based TCP-friendly congestion control mechanism-TFRC, studies its basic structure and some key details. In order to improve its performance of low jitter for real-time application, it provide a new algorithm of TFRC by using the jitter as a warning congestion signal. Simulation on ns verifies the new algorithm.This thesis completed a small-size and practical net-video transmission system, by adopting the techniques above and using USB camera as the video collection equipment. RTP and RTCP used in cooperativity can provide the data real-time transmission and QoS service to satisfy the requirements of the delay and the packet lost for the network video data real-time transmission.