iPerf CWND

Hi,

I am working on linux hosts and iPerf 3. I like how iPErf3 shows retransmissions. I am trying to increase my Cwnd and everytime i set bandwidth it never goes above 500Kbytes?

[centos]# iperf3 -c 10.196.250.14 -w 30m

Connecting to host 10.196.250.14, port 5201

[ 4] local 10.198.70.254 port 39240 connected to 10.196.250.14 port 5201

[ ID] Interval Transfer Bandwidth Retr Cwnd

[ 4] 0.00-1.00 sec 150 MBytes 1.26 Gbits/sec 140 434 KBytes

[ 4] 1.00-2.00 sec 114 MBytes 954 Mbits/sec 0 589 KBytes

[ 4] 2.00-3.00 sec 112 MBytes 944 Mbits/sec 0 711 KBytes

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I have tuned TCP as well ?