TCP Congestion control, shape TCP traffic so that receiver does not get over flooded by sender high rate of TCP packet transfer. TCP Congestion get managed through a field in TCP header known as Window. You can notice , in the following image , windows field of tcp header is set to 8192
What does this value doing in TCP congestion control ?
The TCP sender use cwnd (Congestion Window) in controlling its transmission rate based on feedback it gets from the receiver. In simple words you can say tcp congestion window is estimate of how much maximum packet receiver can accept without losing any packet .
In Linux more than one algorithm exist for tcp congestion control. I issued following command to get list of algorithm exist on my CentOS6.3 system
So my my system there are two tcp congestion control method are present , as you can in above image there algorithms are cubic and reno
This is apparent that that only one among these two is currently applicable and working as tcp congestion control method
So here cubic is in place .