APU2 routing speed NetBSD

[76nemo76%gmx.ch@localhost]

Hi All,
     I am working with an APU2 board (4gb, 3 lan and AMD CPu 1Ghz
you can see specifications here http://www.pcengines.ch/apu2.htm)
to make a router/firewall.

Before choosing the OS I want to use I have done some benchmarks.
My first benchmark is:
             1) Copy of a big file (17GB) compressed with gzip
                from a Windows 10 machine to a Windows 8.1 machine.
                This is done by using CIFS on Windows. Each machine
                is at one side of the router.

The results are strange:
            With OpenBSD and Linux (alpine linux 3.4) I get
            the maximum speed (112Mbytes/sec) while with NetBSD
            the speed is limited to 70Mbytes/sec.

All the hardware is identical and all the router OS are installed on the APU2.
To do the tests, I simply reboot the router and I choose an
other OS.

Do you have an idea why there is a such big difference? Should I
tune some specific network parameters on NetBSD?

I have done a second benchmark by transferring the same file 
with ftp, but this time the second machine was a Linux server 
(running on the same hardware as the Windows used for
the CIFS transfer) and I get similar
differences (80-85Mbytes with Linux Router,50-55Mbytes
with NetBSD).

The benchmarks were run without any firewall. 


Thank your for your help,

best regards,

Alan