How can you defend your service from a distributed denial of service attack? The Answer is at the grocery store. Distribute your service to force your adversary to divide his forces or be ineffective.
The Challenge of Distributed Denial of Service Attacks
A Distributed Denial of Service attack (DDoS) aims to flood a computer providing a service (e.g. a web server) with so many requests from so many different sources that your server is overloaded and service is either degraded (i.e. very slow) or denied (by crashing the server). This is similar to a website running slowly when it is being used a lot by legitimate users, except that the degradation is deliberate and intends to deny legitimate users access to the service temporarily or permenantly.