I have 2 machines connected to a switch via 1Gb Ethernet cables. I am sending TCP traffic from one host to another. I wanted to see how many re-transmitted packets are there from sender side using netstats. to my chagrin, there was not any re-transmission. Should not the cwnd grow too large and packet loss should occur, resulting in re-transmission. Need expaination.
It doesn't work as you are expecting.
The cwnd/rtt rate does increase but it can't get any further than the physical transmision speed on the underlying interface can process.
Your expected re-transmissions never show because the output queue throttles itself before that point is reached. The data-delay caused by the throttling happens in the application output buffer which is not visible in the information netstat shows.