Some update: With CRC offloading I get 750 instead of 720mbps TSO remains default , everything else default Then when I try a 64k windowsize and at least 2 iperf3 streams I am finally seeing a mixed total result of 930mbps But with one iperf3 stream and various window sizes all I am getting is around 750 (CRC hw offloading) or 720 (no CRC hw offloading) Any guesses? At least its doesn't appear to be a hardware problem but I think a client should be capable of getting 1gig in a single stream?