you are right, that the dlsd is doing much more than the VDSL stuff. The only reason why I tried to do something on top of freetz was that I didn't want to brick my only box. It is easy to unload the AVM closed source modules and load other (own) modules for testing. If I was able to control the VDSL modem it should be possible to establish a VDSL connection with other standard linux tools. After that I would be brave enough to try to install openwrt on the box and get rit of the closed source AVM firmware. I am a little bit paranoid and I want to be able to have a firewall with connection tracking running on my box, which is impossible with the AVM VDSL modules because enabling connectin tracking in kernel makes the modules incompatible with the kernel. Since there seems to be no byable hardware with VDSL2 support I have to use the Fritz Box to handle the VDSL an connect a router supported by openwrt to one LAN port of the Fritz Box all other ports are unused (because I can not trust them, the firewall is on the openwrt router). This is not the best possible setup.