DNS attacks can be particularly harmful because without DNS, your website, applications, email, etc. are rendered useless.
The best way to avoid any disruption from a DDoS attack is to be prepared for it. Talk to your DNS provider and ask about their mitigation techniques, and if you currently are doing everything in-house or are relying on your ISP or a firewall, evaluate your situation.
Download this white paper to learn how to recognize the early signals of a DDoS attack and how to survive it.