currently there is a problem with the connection to RWTH and therefore DFN. We don't what is wrong with it, but we are not alone.
Our systems are working, our internal connection to this site works, that's why you can read this Page.
We will update this post if necessary.
UPDATE #1 18:56: There is a problem at RWTH, they know and they are working on it. Please look at Facebook and Twitter for their maintenance ticket, our Bot posted the link to the ticket.
UPDATE #2 19:28: Everything seems to be working again.