In the improved algorithm, it introduced a kind of improved MAC frame-MFC, making SCTP can distinguish link losses and network congestion, maintaining the network congestion window in a relatively stable size, ensuring the reliability of data transmission. In the algorithm, when the number of timer is 4, MAC layer of the sender will generate MFC and will this frame sent up to SCTP protocol, SCTP notice a frame of the current data block which is failed to send in the MAC layer, the reason for failure is defined as the high bit error rate of wireless network instead of network congestion. When MFC message reach to the transport layer, SCTP protocol will extract the useful information of MFC message, then trigger retransmission of identification of loss data block in the MFC, But the size of the congestion window won't reduce to led to reduce transmission throughput rate. MFC frame increases the ID of data stream in the upper layer, the number of current data blocks and other control field. Frame format as shown in figure 3: