Let's say I have a root domain of "mysite.com". That domain and its sub-domains have DNS served by an external service - let's call them Setwork Nolutions. If this external company is hit with a DDoS attack, my interally-hosted websites under this domain are no longer accessible at "mysite.com" or "*.mysite.com", even though the website(s) is/are fully up and operational.

How can I mitigate such a problem so as to keep end users happy?

The only solution others at my company have come up with is to create a second domain - i.e. "mysite2.com", and host its DNS at another company, and then communicate to all end users that this is the website they should use. I think this is ridiculous, and just leads to a bunch of other problems.

I'd like to find a solution where we can point to the same website with the same URL without the original DNS host being operational.

Any thoughts?