Das hat mir der Support meines Servers geschrieben :
No, this is due to peering between your ISP and our datacenter.
You cannot expect to get 400mbps on a single thread from a home line. First of all you definitely need to use multithreaded downloads
Make sure you use a ftp client that supports multiple simultaneous downloads and multisegmented downloading, to maximize your download speeds. We highly recommend cuteftp pro for this:
http://help.globalscape.com/help/cuteftppro8/Multi-part_transfers.htm
Secondly, Go to speedtest.net, and from the map, choose the test server in Rotterdam, The Netherlands, that says "Rotterdam, Interactive 3D". This is a test server located in our datacenter. Please run the speedtest, and check the result. You will probably get a result near the speed you are getting from our servers.
Just because your ISP sells you 400mbit line, this does not mean that they have the necessary international capacity to support such speed. Possibly, you will get that speed, peer to peer from other peers of your ISP, or within your country. But not from an outside location.
Nevertheless, what you get, is half of your home line, and it is pretty good. Try to use multisegmented downloading, and you will probably make it even better.
Best Regards,
Tony