What does TFRC mean?

Summarize TFRC: TCP-friendly rate control (TCP-friendly rate control algorithm).

Real-time streaming media service needs a stable network transmission rate, so that it can be played smoothly at the playback end and achieve the desired playback quality of users. At present, Internet data transmission services are basically based on TCP. TCP adopts the congestion back-off mechanism of halving the rate, which is easy to cause the rate fluctuation of data flow to be too large, which is very unfavorable to multimedia transmission. The research shows that when TCP/IP protocol is used in the transmission process, when there are many users, the playback will be delayed and discontinuous. However, UDP has no congestion fallback mechanism. In the congested network environment, UDP flow will seize a lot of network bandwidth of TCP flow, and its own packet loss will increase rapidly, which may bring the potential danger of system congestion collapse. Therefore, neither TCP nor UDP can meet the demand of real-time streaming media service. With the rapid growth of multimedia real-time services on the Internet, it has become an important topic for Internet transmission to study a transmission protocol which is suitable for multimedia transmission, has congestion backoff mechanism and can share bandwidth fairly with TCP protocol.

TFRC is such a protocol. It is based on mathematical model, and the sender adjusts the sending rate of data stream according to the network environment, so as to achieve the purpose of congestion control. Under the same conditions, the throughput of TFRC flow is roughly the same as that of TCP flow, so it can share the network bandwidth with TCP*** "fairly". On the other hand, TFRC's throughput is stable and jitter is small, so it is more suitable for applications such as telephone and streaming media, which require high transmission rate smoothness.

TFRC is a congestion control mechanism of TFRC, which is suitable for applications with fixed packet size. According to the quality of the network environment, it adjusts the data transmission rate by adjusting the number of packets sent per second. TFRC is a receiver-based mechanism, which calculates congestion control information, such as packet loss event rate, at the receiver.

The congestion control mechanism of TFRC is as follows:

* The data receiver measures the packet loss event rate p, and then feeds it back to the sender together with the timestamp;

* The sender uses the timestamp in the feedback information to measure the cycle time RTT；;

* Substitute the packet loss event rate P and RTT into the throughput equation of TFRC, and get a transmission rate through calculation;

* Then, the sender adjusts its data transmission rate according to the calculated rate.