Mostly posting because this had the first lulzy Slashdot comment I've seen in years:

how do you cope with DDoS?

Send all packets back where they came from. They are raping our servers. They flood our network routers. They bring in DOS. Some of them, I suppose, are nice packets.

I love network packets, I have thousands and thousands sent to me every day. But these packets were sent by nasty, nasty criminals. You know what we did in the old days with these criminals. They are drowning our servers in packets.

What are the best tools to protect yourself

Build a firewall, and let the hackers pay for it.

and what to do when the attack is on?

Vote for Donald J. Trump.