[shame] how could i miss that.
it can reach up to 4MB/s under 240ms latancy network after i set the buffer size to the maxium value (1024KB per 240ms). but it still need to run the command below to enable the tcp window tuning every some minutes or it will go back to xxKB/s again
Code:
netsh interface tcp set global autotuninglevel=disabled
netsh interface tcp set global autotuninglevel=normal
that should be a bug in the os.
anyway thank you for your reply