Because of network performence problems I have to disable "TCP Large Send Offload" and "TCP Checksum Offload" at the NIC of the Hyper-V manager (not at the physical NIC). I tested this at a full installation and it seems to help. But I plan to use the Core installation.
How to disable the TCP Offload [...] there without the device manager (which is not available at the core installation (a grate function, really...))?
For the NIC, you'll need to modify the registry. There is an earlier thread on changing the binding order, which has the information to get you to the right place.
There are some settings for TCP/IP, go to "netsh interface tcp" and then run "set global" and you'll see all the options for some of the advanced TCP/IP configuration. One of those may help.