Fast Recovery (2)


Congestion estimation by Reno TCP 
If packet loss was found by Retransmit Timeout,
Congestion is serious.
Windowsize should be set to minimum value and do Slow-start.

If packet loss was found by Duplicate ACK,
Congestion is not serious.
Because..
At least 3 packets could arrive at the receiver after packet loss.
At least 3 packets has left the network, so there may be a chance to transmit a packet
.
So, windowsize is set to half of current value and do Congestion Avoidance.