With the rapid development of network communication technology and applications, more refined and differentiated data transmission requirements of applications are put forward. However, the low flexibility of traditional network transmission protocols makes it unable to meet the differentiated requirements of various applications, and thus there is an urgent need to study differentiated reliable transmission control protocols for future scenarios. This study proposes a differentiated reliable transmission protocol and focuses on a reliability-based differentiated reliable transmission congestion control mechanism. Different congestion avoidance and congestion recovery strategies are designed for different reliability differences, and the bandwidth estimation strategy is employed to accurately adjust the congestion threshold. Experiments verify that the differentiated reliable transmission congestion mechanism has greater improvement in transmission efficiency than the packet loss and delay-based congestion algorithms and at the same time can achieve good fairness.