Thursday, February 9, 2012

TCP Congestion Conbtrol mechanism

1, slow start -  here.

2, congestion avoidance - here.

3, fast retransmit -  when three or more duplicate ACKs are received, the sender does not even wait for a retransmission timer to expire before retransmitting the segment (as indicated by the position of the duplicate ACK in the byte stream). This process is called the Fast Retransmit algorithm.


4, fast recovery -  TCP sender has implicit knowledge that there is data still flowing to the receiver. Rather than start at a window of one segment as in Slow Start mode, the sender resumes transmission with a larger window, incrementing as if in Congestion Avoidance mode. This allows for higher throughput under the condition of only moderate congestion.