It’s not that easy to get trafic shaping done with Linux especially when it comes to inbound traffic. After some serious research i found this howto which is a excellent starting point. The supplied script can be easily customized and works pretty good. If there’s interest i can post my version for incoming traffic only.
You have to apply the IMQ patch (can be found here) to your kernel to get this working. IMQ is necessary because Linux can only limit outgoing traffic with builtin kernel settings.