Thank you for the explains concerning my post....
now, given that i have unfortunately found this problem ONLY with R3 Nas enterprise (specially with the version 5.0) and NEVER with the XSR Enterprise (specially with the version 3.0 bd. 1660-1666, for me the Open-e NAs with the highest performance that i have try so far!), i would to know if is possible that the "drivers" included in the R3 software for my NIC, aren't updates and offer low performance.
It could be the NICs of the system has 2 NIC's and only one is being used, make the other that is not being used - inactive. Not sure if this could be the same as yours but there is known bug with e1000 driver when there is active NIC with cable unplugged. It very often leads to lack of memory so it has influence on performance. Or try with different NIC.
I will try with other NICs (but which for broadcast use??) but, for correct information, i've also try to connect two clients simultaneously in the available ports, but the result is the same.
Do you know if the NICs i'm using request a particular setting to function properly?
You can try to force the settings for the Intel nic's in the console accessing it by ALT+CTRL+T->Modify driver options select e1000 option and choose AutoNeg. Set this value to 32.
Other vaules you can try are listed from the Intel link below.